Heat a saucepan over medium heat. Once hot, add the oil. Saute the garlic and shallot until golden brown. Add in the spinach, sauté until wilted. Then remove from the heat. Stir in parmesan and season with salt and pepper to taste.
Spoon the filling into the mushrooms. Arrange the stuffed mushrooms on a foil-lined baking sheet.
Bake until the mushroom caps are tender (approximately 20 minutes). Remove from the oven and serve immediately.