In a small skillet, heat 1/2 T olive oil over medium heat until shimmering. Add 1/2 c sliced mushrooms. Saute until limp and browned, 5-8 minutes. Remove from heat and set aside.
In a soup pot, heat remaining 1 T olive oil and butter until butter melts and foaming subsides. Add onions and saute 1-2 minutes until beginning to soften. Add garlic, mushrooms, salt, pepper, thyme and bay leaf. Cook until mushrooms collapse and exude liquid, about 8-10 minutes.
Add chicken broth, beef broth, Worcestershire sauce and sherry. Simmer 10 minutes. Remove and discard bay leaf.
Add cream cheese and half-and-half. Stir until cheese is melted. Using an immersion blender, puree the soup until smooth. Simmer an additional 10 minutes. Serve with a few pieces of sauteed sliced mushrooms on top.