In a large slow cooker, stir together chicken, onions, tomato sauce, 1 tbsp. paprika, bouillon, garlic salt, and 2 tbsp. butter.
Cover, and set slow cooker to 'low'. Cook for about 6 hours, or until chicken is tender.
In a small bowl, combine flour and remaining melted butter.
Whisk into the slow cooker.
Cover, and set slow cooker to 'high'.
Cook for 15 minutes, or until sauce is thickened.
Turn off slow cooker, and remove from heat.
Stir in remaining paprika, and sour cream.
Salt & pepper to taste, and serve hot over rice or noodles.