In a large pot, over medium-high heat, melt 2 tablespoons butter. Add in carrots, celery and onions. Saute until just starting to soften, about 3 - 5 minutes. Add mushrooms, garlic and remaining butter. Continue cooking until mushrooms are tender, another 3- 5 minutes.
Add broth and worcestershire sauce to mushroom mixture. Stir. Bring to a boil over medium-high heat, then reduce heat and simmer, uncovered, for 30 minutes, stirring occasionally.