Spinach and Mushroom Frittata

Ingredients

• 6 large eggs
• 1/4 cup milk
• 1 tablespoon olive oil
• 1 small onion, diced
• 8 ounces mushrooms, sliced
• 2 cups fresh spinach
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1/4 cup shredded cheddar cheese