preheat oven to 400°. Grease a shallow baking dish with some of the olive oil. Dip mushrooms into lemon juice, place in pan stem side up, making sure they fit tightly in the dish to keep the caps from overturning.
Finely dice the mushroom stems. Heat oil in a sauté pan over medium heat and cook chopped stems with the garlic, until the garlic turns Golden. Stir in the pine nuts, bread crumbs, and red pepper flakes. Season with salt and pepper. Remove from heat and allow the mixture to cool. Fill the mushroom caps with stuffing and bake, uncovered, for 15 to 20 minutes. Serves six.