Use a 6-quart slow cooker. With a damp cloth or paper towels, clean the mushrooms, wiping away any visible dirt. Cut each mushroom in half, or in quarters, depending on size (each piece should be about 1 inch across). Add the mushrooms to the slow cooker insert and toss with the rest of the ingredients.

Cover and cook on low for 4 hours or on high for about 2 hours. Stir well and serve with a slotted spoon as a side dish, or spread out on a platter with toothpicks as an appetizer.