Chop the mushroom stems, dice the onions and celery. In a small saute pan over medium heat add the olive oil. When hot add the mushrooms, onions, celery. Season with salt, pepper and red pepper flakes. Sauté for about 4 minutes until the vegetables just start to soften. Add the garlic & saute until it becomes fragrant about 30 seconds, remove from heat. Allow to cool.