This is NOT authentic Indian food. This is a recipe my mother used to make, veganized by me. It's an excellent comfort food, not very fancy at all, but cheap, fast, easy and good. Admittedly the 'sauce' is a little runnier in the vegan version, but otherwise, I like it a lot better.
Start the rice first and it should be done at around the same time as the rest of the recipe.
Chop the onion small and the celery the way you would for a macaroni-type salad (i.e. crosswise, small). Sautee these in some oil, about three minutes on medium-high, then add the veggie chicken (or, the equivalent amount of seitan or frozen, defrosted firm tofu cubes). Cook till the "chicken" is done. It should be golden brown, tender and chewy. You could also microwave these separately from the sautéing veggies, but it tastes better made together.
While your "chicken" and celery and onion are cooking (make sure to stir them up occasionally) melt the margarine and butter in a pot and dump in curry powder to taste. It's ready when it starts to bubble a bit and/or becomes slightly thicker. Or when you say it's ready, I guess.
When everything is done, simply dump it together. It should smell lovely and taste even better.