Meanwhile, thinly slice the mushrooms. In a large skillet, cook the butter over high heat until lightly browned, 2 minutes. Add the remaining 2 tablespoons of olive oil and the mushrooms and cook undisturbed until the mushrooms are browned on the bottom, 2 minutes. Continue to cook, stirring occasionally, until browned all over, 10 minutes. Add the shallots, garlic and thyme, lower the heat to moderate and cook until the shallots are tender, 5 minutes. Add the water and scrape up any browned bits from the bottom of the pan, then cook for 3 minutes longer. Season the mushrooms with salt and pepper and remove from the heat.