Place the red bell pepper and yellow bell pepper in a large pot with 1/4 teaspoon butter, and cook, stirring constantly, until peppers are slightly charred. Mix in tomatoes, onion, garlic, and chicken broth. Season with salt, sugar, cloves, oregano, and basil. Bring to a boil, and cook 20 minutes, until tomatoes are soft.
Mix the milk and cornstarch in a small saucepan, and stir until smooth. Place saucepan over medium heat, and stir in remaining 1/2 teaspoon butter. Continue to cook and stir until thickened. Mix into the pot with vegetables.
Strain about 1/2 the vegetables from the soup and transfer to a blender. Blend until smooth, and return to the pot. Bring soup to a boil, reduce heat to low, and simmer 5 minutes. Remove from heat, and let sit about 5 minutes before serving.