Melt butter in a large Dutch oven over medium-high heat. Sauté onion, red and green peppers until tender. Add garlic and the remaining seasonings. Reduce heat and sauté an additional 1 to 2 minutes. Add chicken to pepper mixture and sauté another 2 to 3 minutes. Add beans, stewed tomatoes, and tomato sauce and tomato paste to the mixture. Bring to a low boil. Reduce heat and simmer, uncovered, for about 30 minutes or until chili thickens.