Vegetarian Quiche | Cooking Professionally

Ingredients

• 2 tablespoons extra-virgin olive oil
• 8 ounces fresh mixed mushrooms, such as wild cremini, shiitake, button, and/or oyster mushrooms, sliced
• 1 1/2 cups sweet onion, thinly sliced
• 1 tablespoon garlic, thinly sliced
• 8 cups fresh baby spinach, coarsely chopped
• 6 large eggs
• 1/4 cup whole milk
• 1/4 cup half-and-half
• 1 tablespoon Dijon mustard
• 1 tablespoon fresh thyme leaves, plus more, to taste, for garnish, divided
• 1/4 teaspoon salt
• 1/4 teaspoon ground black pepper
• 1 1/2 cups Gruyère cheese, shredded