Make the roux first by adding butter into a fry pan and melt it down. Then add the flour and completely cook it.
Add the garam marsala, curry powder and optional cayenne to complete the paste.
In a medium pot, heat up oil, and saute down onions, potato and carrots.
Add apples, chicken stock cube and 50% of the prepared roux into the mix and fill it with water. Let it simmer for at least 30 minutes on a medium heat and stir occasionally.
Season your meat cuts with salt and pepper, then crumb it with flour, egg, and panko (in that order). Repeat crumbing until desired effect.
Deep fry your crumbed meats until golden brown. Let it drain and rest.
After your curry has simmered - add in additional roux (if required) until the curry is of thick consistency.
Serve tonkatsu, curry over rice.