Put chicken, grind roux and yogurt into a re-sealable bag. Mix and marinade for 15 minutes.
Heat vegetable oil in a large stockpot and sauté onion, garlic, ginger, and mustard until fragrant.
Add sliced onions and sauté until translucent.
Add water and bring to a boil, skim off any white foam from the top of the liquid. Once water starts boiling, reduce heat and simmer at medium-low heat for 5 minutes.
Meanwhile, in a skillet, heat ½ tablespoon of vegetable oil and cook green bell pepper. Once done, remove from skillet and set aside.
In the same skillet, heat 1½ tablespoons of vegetable oil and cook marinated chicken.
Remove stockpot from heat and stir in remaining curry roux. Simmer and stir for 5 minutes, add green bell pepper and continue simmering for a little longer.
Serve over hot cooked rice and garnish with spices over curry.