Melt butter in a large soup pot over medium high heat. Add potatoes and carrots and cook for a coupld of minutes. Stir in flour and curry powder and cook 5 more minutes. Add stock, mix well and bring to the boil. Simmer about 1/2 hour.
Add pre-cooked rice, thyme, salt and pepper. Simmer 10 minutes until thickened.
Serve with a crusty bread or naan.
Add other vegetables to your liking, e.g. onions, celery, peas.