Melt butter with olive oil in the same Dutch oven/stockpot over medium heat. Increase temperature to medium-high and add mushrooms. Spread mushrooms into an even layer and let cook for cook for 3 minutes without moving. Add shallots and cook and stir an additional 3-5 minutes, until all the liquid is evaporated and mushrooms are browned. Add
soy sauce and garlic and cook 30 seconds.