Place the mushrooms, ale, and garlic in a large skillet. Simmer the mushrooms until tender,
about 5 minutes. Lift the mushroom out of the
skillet with a slotted spoon and set in a bowl. Simmer and reduce the liquid in the skillet to about 2 Tbsp., then pour over the mushrooms. Combine remaining ingredients in a small bowl, pour over mushrooms, and toss to combine. Cool to room temperature, cover, and marinate in the refrigerator for at least 4 hours.