Heat oil and curry powder in a large pot over medium-high heat for 2 minutes until it turns brown. Be careful not to burn.
Stir in onions and red bell pepper, and cook for 2 minutes.
Add garlic and cook for 1 more minute.
Add chicken, tossing lightly to coat with curry oil.
Season with salt and pepper to taste. Reduce heat to medium, and cook for 7 to 10 minutes, or until chicken is no longer pink in center and juices run clear.
Pour coconut milk, tomatoes, tomato sauce, sugar, and crushed red pepper into the pot, and stir to combine.
Add cauliflower and mushrooms. Simmer, uncovered, stirring occasionally, approximately 30 to 40 minutes.
Serve over rice.
To Store
You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days or in the freezer for a month.