Katsu sando

Method

1. Take the cutlets out of the fridge while you set up. Cold is fine and correct here, but fridge-cold dulls the flavour, so ten minutes on the counter helps.
2. Butter all four slices right to the edges. The butter is not for richness, it is a seal: it stops the sauce soaking into the bread and turning the sandwich to mush before you eat it. Spread mustard over the butter on two of the slices.
3. Brush or spoon tonkatsu sauce generously over both sides of each cutlet. Be heavier-handed than feels right, since the bread absorbs a lot and cold food reads as under-seasoned.
4. If you are using cabbage, lay a thin even layer on the mustard slice. Keep it thin. A tall pile of cabbage makes the sandwich impossible to cut cleanly and slides out when you bite it.
5. Set a cutlet on top, trimming it so it reaches the edges of the bread. Overhang gets cut away with the crusts and wasted, so trim the cutlet rather than letting it hang. Close with the second slice, buttered side down.
6. Wrap the sandwich tightly in baking parchment or cling film and press it under a plate for 5 minutes. This is what makes the cross section look like the one in the shop window.
7. Unwrap, cut the crusts off all four sides with a long serrated knife, wiping the blade between cuts. Then cut the sandwich into halves or thirds. Serve at once, or rewrap and take it out with you.

Notes

• The bread. Shokupan, the square Japanese milk bread, is soft, faintly sweet, tight-crumbed, and effectively unavailable in Germany. Toastbrot is the closest common option, and the thick-cut American Sandwich style loaves from Golden Toast or Harry are what to reach for. Do not toast it. If you can find Buttertoast, better still. Brioche is too sweet and too eggy, and any Bauernbrot, Vollkorn, or sourdough is completely wrong: the point is a soft neutral wrapper that disappears against the crunch of the cutlet.
• This is the leftover play. Katsu sando exists because cold katsu is good and reheated katsu is not. Fry an extra cutlet or two whenever you make chicken katsu and this is lunch the next day. A cutlet keeps two days in the fridge, wrapped loosely so the crust does not sweat.
• If you only have hot katsu, let it cool to room temperature on a rack before building the sandwich. Hot katsu steams the bread from inside and the sandwich collapses.
• Sauce. Make the tonkatsu sauce from the chicken katsu recipe: Worcestershire, ketchup, soy sauce, and sugar. Bulldog sauce is not something you will find in Schwäbisch Hall. Japanese Kewpie mayonnaise on the bread alongside the butter is a common addition and worth it if you have a jar.
• Pork or egg. Tonkatsu made from pork loin is the original. The other convenience-store classic is tamago sando, chopped hard-boiled egg with mayonnaise, and the two travel well together.
• Packing it. Wrap tightly in parchment and cut through the paper with the sandwich still wrapped. It holds its shape and does not leak in a bag.

Sources used

• Just One Cookbook: Katsu Sando
• Just One Cookbook: Tonkatsu Sauce