Melt 1 tablespoon of the butter in a large pot over medium heat. Cook the onion with a pinch of salt for 8 to 10 minutes until soft and golden at the edges. Add the garlic and ginger for the last minute.
Season the chicken with salt, push the onions aside, and sear the chunks for 2 minutes per side. They do not need to cook through yet.
Add the remaining butter, then sprinkle in the flour and curry powder. Stir for 1 to 2 minutes so the flour cooks and everything turns into a sandy paste coating the chicken. This is the roux, made in place.
Pour in the stock gradually, stirring so no lumps form. Add the carrots, potatoes, soy sauce, ketchup, and honey.
Simmer uncovered for 15 to 18 minutes, stirring now and then, until the potatoes are tender and the sauce coats a spoon. If it gets too thick, loosen with a splash of water.
Taste for salt and serve beside short grain rice, with fukujinzuke pickles if you have them.