In a 5-1/2 to 6-quart Dutch oven cook mushrooms, shallots, and carrots in hot butter about 15 minutes or until mushrooms are tender; stir occasionally. Stir in flour, thyme, garlic powder, 1/2teaspoon each salt and black pepper and, if desired, crushed red pepper. Add broth all at once. Cook and stir until soup is slightly thickened and bubbly.
Stir in artichokes, tomatoes, and bay leaf. Simmer, covered, for 15 minutes. Stir in half-and-half; heat through. Discard bay leaf. Top with green onions. Makes 10 appetizer servings