Heat saute pan; add the olive oil and butter. Add the mushrooms and season to taste with salt and pepper. Saute briefly, add the shallots and garlic and continue to sauté until lightly golden brown. Deglaze with the sherry, add the stock and cream and bring to a boil. Reduce slightly, add the thyme and correct seasoning if necessary. Puree with a hand wand or in a blender. Adjust seasoning again if necessary. Serve hot in large cups with steamed milk on top for the cappuccino effect