Japanese curry sauce

Method

1. Make the roux first. It wants your whole attention and nothing else can have it at the same time. Melt the butter in a small heavy saucepan over medium-low heat, whisk in the flour, and keep it moving for 20 to 25 minutes. It goes pale, then sandy, then the colour of peanut butter, and it smells like toasted biscuits. It darkens fast at the end, so stand there. A scorched roux is bitter and there is no saving it.
2. Take the pan off the heat and stir in the curry powder, cinnamon, nutmeg, cardamom, fenugreek, black pepper, cloves, cayenne, and salt. The residual heat blooms them without cooking them hard. Stir for a minute, scrape the roux into a bowl, and set it aside. It stiffens as it cools, which is what you want.
3. Heat the oil in a wide heavy pot. Add the onions with a pinch of salt and cook them over medium heat for 25 to 30 minutes, stirring every few minutes, until they collapse and go properly brown at the edges. This is the single longest step and the one people cut short. Half the colour and most of the sweetness of the finished sauce come from here, not from the spices.
4. Add the garlic and ginger and cook for a minute, then the grated apple, and cook two minutes more until it stops smelling raw.
5. Pour in the stock. Add the soy sauce, tonkatsu sauce, and honey. Bring to a simmer, skim the foam, and let it go uncovered for 20 minutes. You want the volume down a little before the roux goes in.
6. Ladle about 250 ml of the hot liquid into the bowl of roux and whisk it smooth, then pour that back into the pot while stirring. Slackening the roux first is the only reliable way to avoid lumps.
7. Simmer gently, uncovered, for 12 to 15 minutes, stirring often and scraping the bottom. Thick sauce insulates the base of the pot and will catch if you leave it. Stop when it hits the target in the notes below.
8. Take the pot off the heat and stir in the garam masala. This is its own step for a reason: cinnamon, cardamom, and clove carry their aroma in volatile oils that boil off under sustained heat, so a blend added at the start ends up as background and the same blend stirred in at the end sits at the front of the mouth. This is the step that gets you the cinnamon and nutmeg you remember.
9. Let it stand 10 minutes, then salt it properly. Homemade roux carries almost no salt where a shop block is mostly salt and flour, so this is where an under-seasoned curry gets fixed. Taste it on a spoonful of plain rice, not off the spoon, because rice mutes salt.
10. Serve, or cool and portion for the freezer.

Notes

• Why a scratch roux and not a block. The published S&B Golden Curry label reads wheat flour, oils, sugar, salt, curry powder at 7.7 percent (turmeric, coriander, cumin, fenugreek, orange peel, spice), flavour enhancers, colour, spices (pepper, garlic, celery seed, mustard), malic acid. There is no cinnamon and no nutmeg declared anywhere on it, and Ottogi’s Korean curry powder declares none either, so no block and no Korean powder can be the thing you are remembering. If you want those two spices at the front, they have to be line items you control, which means building the roux yourself.
• Dial it in. This is the point of the recipe. Cook it three times, changing only these two numbers, and you will find your memory. Low: 3 g cinnamon, 1.5 g nutmeg. That is roughly where a good scratch roux normally sits, warm but in the background. Middle: 6 g cinnamon, 3 g nutmeg, which is what is written above, where both are clearly identifiable in the first mouthful. High: 10 g cinnamon, 5 g nutmeg, where the sauce reads as a warm-spice curry first and a savoury curry second. Keep everything else fixed each time. If the high setting tips into tasting like a Christmas market, pull the cloves out before you touch the cinnamon, because clove is what pushes a curry into baking territory fastest. A 5 cm cassia stick and one star anise dropped into the pot at step 5 and fished out before serving add a rounder, less powdery version of the same note.
• The garam masala ratio. Roughly one part garam masala to four parts Japanese curry powder, added off the heat. Japanese curry powder is mostly turmeric, coriander, cumin, and fenugreek, with warm spice at maybe one percent of the blend. Adding a quarter of its weight in garam masala takes warm spice to the high teens as a share of the total spice load. That is a different dish, not a tweak.
• What you may actually be chasing. Osaka spice curry, スパイスカレー, is a Kansai style that grew up in the 2000s outside the standard recipe tradition. Its core spices are turmeric, coriander, cinnamon, cumin, and black pepper, and each shop builds a signature around one chosen spice. A shop whose chosen spice is cinnamon produces exactly the thing you are describing, and it will never match a home recipe for kare raisu, because it is not trying to be one. That is the most likely reason you have eaten it and never found it written down.
• Consistency, and how to test it. The target is thick enough to mound. Drag a spatula across the bottom of the pot: the track should stay open for about two seconds and then close slowly. If it closes instantly it is too thin, and if it does not close at all it is too thick. On a plate it should hold a clean edge against a mound of rice for a minute rather than run to the rim, and on the back of a spoon a finger line through it should stay open. What thickens it: more simmering uncovered, more roux (reckon 40 g of roux per 250 ml of liquid), and simply cooling, since it sets noticeably as it drops below hand temperature. What thins it: stock, water, dashi, and anything watery added late. It always looks thinner in the pot than it will be on the plate, so stop a shade before you think you should.
• The depth-builders, honestly. Grated apple does something real, and not for the reason usually given. It brings acid and pectin as much as sweetness, and the pectin helps the sauce hold together. Keep it. Honey rounds off the edge of the spice at the small quantity used here and is worth the two seconds. Tonkatsu sauce is the most useful of the lot: it is already a cooked fruit and vegetable sauce with vinegar, umami, and sweetness balanced, so it does in one spoon what three separate additions would. A square of dark chocolate at 2 to 3 g is not folklore, but it is close: it darkens the colour and adds a trace of bitterness, and blind you would struggle to name it. Instant coffee, half a teaspoon, does the same job as the chocolate and is more obvious about it, which some people like and some do not. Neither one fixes a curry, and both are frequently used to cover for onions that were not browned long enough. Brown the onions properly and you will not miss either. The one that is genuinely folklore is the claim that any of them make the curry “richer”: what makes it rich is the fat in the roux and the sugar in the onions.
• Portioning and freezing. Cool the sauce to room temperature, then divide it into 250 ml portions, which is one plate of curry rice or the base for one bowl of curry udon. Flat freezer bags laid down flat freeze faster, stack better, and thaw in a bowl of water in twenty minutes. Screw-top jars work but leave 2 cm of headspace. It keeps four months frozen and five days in the fridge, and it is better on day two either way. Reheat gently with a splash of water, because it thickens further in the freezer and will catch on a hot pan if you rush it.
• Three routes from one batch. Over rice with a sliced chicken katsu leaned against it, poured beside the cutlet and not over the crust. As plain curry rice, with fukujinzuke at the edge. Or thinned roughly one to one with dashi, given a small starch slurry, and poured over udon, which is the kare-udon recipe. The sauce is deliberately thicker than a curry you would eat straight from the pot, because every one of those three uses either sits it against rice or dilutes it.
• Adding protein and vegetables. This is the sauce alone, so nothing in it needs a set cooking time and it never falls apart on reheating. To make it a full curry, brown 600 g of chicken thigh or beef chuck in the pot before the onions, set it aside, return it at step 5, and add 400 g of waxy potato and 200 g of carrot in the last 20 minutes of that simmer. Do not freeze it with potato in it, because potato goes grainy and watery in the freezer. Freeze the sauce plain and add the potato when you reheat.
• Shopping in Germany. S&B curry powder in the small red tin is in most Asia-Märkte and every German online Asia shop. A mild supermarket Currypulver plus the garam masala gets you close, since the main gap is orange peel and fenugreek. Garam masala is at any Indian or Turkish grocer and in the larger Rewe and Edeka spice racks. Ground fenugreek is Bockshornkleepulver, sold in Turkish shops and Reformhäuser. Tonkatsu sauce means Bulldog or Kagome, Asia-Markt only, and equal parts ketchup and Worcestershiresauce with a pinch of sugar is a fair stand-in. Buy whole nutmeg and grate it; pre-ground nutmeg loses most of what makes it worth having within a few months, and at 3 g in a pot you will taste the difference.
• Failure modes. Roux browned too fast tastes burnt and no amount of stock hides it. Roux tipped in dry gives lumps that never fully whisk out. A hard boil after the roux goes in can make the sauce grainy, so keep it at a slow simmer. A sauce that tastes flat almost always needs salt, not more spice. And a sauce that tastes of raw flour was not simmered long enough after the roux went in, which needs another ten minutes and nothing else.

Sources used

• Just One Cookbook: How to Make Japanese Curry Roux
• Sudachi Recipes: Homemade Japanese Curry Roux
• Sudachi Recipes: Japanese Curry Using Roux Cubes, with secret ingredients
• No Recipes: Homemade Japanese Chicken Curry from Scratch
• How To Japan: Spice Curry, the New Wave from Osaka
• Ovii: When and how to add garam masala