Name: Caramelized Onion, Mushroom and Spinach Frittata
Prep time: 10 min
Cook time: PT-494792H18M32S
Total time: PT-494792H18M32S
Cuisine: American
Ingredients: 12 large eggs; 1/2 cup half and half, or whole milk with a splash of heavy cream; 1 large onion, sliced; 8 ounces baby bella mushrooms, sliced; 2 to 3 cups fresh baby spinach, stems removed and roughly chopped; 2 cups shredded Gruyere cheese; 2 tablespoons salted butter, divided; 2 tablespoons olive oil, divided; 1 teaspoon sea salt, plust more for the onions; 1/2 teaspoon freshly ground black pepper; 1/2 teaspoon paprika; 1/2 teaspoon dried oregano; 1/2 teaspoon dried thyme; 1/8 to 1/4 teaspoon red pepper flakes, optional

Description

This caramelized onion, mushroom and spinach frittata is filled with sweet caramelized onions, tender mushrooms, fresh baby spinach, and Gruyere cheese. It is an easy, savory recipe for breakfast, brunch, meal prep, or a light dinner.

Ingredients

Scale

12 large eggs
1/2 cup half and half, or whole milk with a splash of heavy cream
1 large onion, sliced
8 ounces baby bella mushrooms, sliced
2 to 3 cups fresh baby spinach, stems removed and roughly chopped
2 cups shredded Gruyere cheese
2 tablespoons salted butter, divided
2 tablespoons olive oil, divided
1 teaspoon sea salt, plust more for the onions
1/2 teaspoon freshly ground black pepper
1/2 teaspoon paprika
1/2 teaspoon dried oregano
1/2 teaspoon dried thyme
1/8 to 1/4 teaspoon red pepper flakes, optional

Cook Mode Prevent your screen from going dark

Instructions

Preheat the oven to 375°F.
Heat 1 tablespoon olive oil and 1 tablespoon butter in a 10-inch oven-safe skillet over medium-low heat. Add the sliced onion and season lightly with salt. Cook, stirring often, for 35 to 40 minutes, until the onion is soft, golden, and deeply caramelized. If the onions start browning too quickly, lower the heat. Remove ¼ cup of the caramelized onions and set aside for topping.
Add the remaining 1 tablespoon olive oil and 1 tablespoon butter to the skillet, if needed. Add the sliced mushrooms and cook for about 5 minutes, or until they have released their liquid and the liquid has evaporated.
Add the chopped spinach and cook for about 1 minute, just until wilted.
In a large bowl, whisk together the eggs, half and half, sea salt, black pepper, paprika, oregano, thyme, and red pepper flakes, if using. Whisk until the mixture is smooth and slightly frothy.
Stir the shredded Gruyere into the egg mixture.
Pour the egg mixture into the skillet over the vegetables. Gently move the filling around with a spatula if needed so the onions, mushrooms, and spinach are evenly distributed. Top with the reserved caramelized onions.
Transfer the skillet to the middle rack of the oven. Bake for 22 to 25 minutes, or until the center is just set. Do not overbake. The frittata will continue to cook slightly as it rests.
Let the frittata cool for 10 minutes before slicing. Serve warm, at room temperature, or with sour cream, avocado, or fresh chives.

Notes

A 10-inch oven-safe skillet works best for this recipe. A larger skillet will make a thinner frittata and may reduce the bake time.
For a potluck or brunch, the frittata can be baked ahead and served warm or at room temperature.
If baking in a disposable aluminum pan, cook the onions, mushrooms, and spinach in a skillet first, then transfer them to a greased 9×13-inch aluminum pan. Add the egg mixture and bake until the center is set. The frittata will be thinner, so begin checking earlier.

Prep Time: 10 min
Cook Time: 1 hr 10 min
Category: Breakfast
Method: Baking, Stovetop
Cuisine: American