Mushroom and Onion Frittata

1 pound sliced fresh mushrooms
1 medium red onion, chopped
3 tablespoons butter
3 tablespoons olive oil
1 shallot, chopped
1 garlic clove, minced
1/2 cup shredded cheddar cheese
1/4 cup shredded Parmesan cheese
8 eggs
3 tablespoons heavy whipping cream
1/4 teaspoon salt
1/4 teaspoon pepper

In a 10-in. ovenproof skillet, saute mushrooms and onion in butter and oil until softened. Reduce heat to medium-low; cook for 30 minutes or until deep golden brown, stirring occasionally. Add shallot and garlic; cook 1 minute longer.

Reduce heat; sprinkle with cheeses. In a large bowl, whisk the eggs, cream, salt and pepper; pour over top. Cover and cook for 4-6 minutes or until eggs are nearly set.

Uncover skillet. Broil 3-4 in. from the heat for 2-3 minutes or until eggs are completely set. Let stand for 5 minutes. Cut into wedges. Makes 4 servings.