Onion Mushroom Gratin

 

Wanting something comforting and creamy to accompany rather plain chicken, I sauteed onions until soft, quickly fried onions in another pan and came up with this recipe that my husband and I enjoyed very much. Easy to make ahead and let sit in the fridge for a day or two before baking. 

Onion Mushroom Gratin

3 medium-large onions, sliced 1/8 - 1/4 inch thick (about 3 cups)

10-12 mushrooms, sliced (about 1-1/2 cups)

2 Tablespoons butter, divided

2 Tablespoons olive oil, divided

1 teaspoon dried thyme

1/2 - 1 teaspoon salt (to taste)

2 - 3 Tablespoons heavy cream

1 cup grated Swiss cheese

2 Tablespoons grated Parmesan

Heat half of the butter and olive in a heavy skillet over medium low heat. Add the onions and saute, letting them slowly soften and sweeten. This should take a good 15-20 minutes. They should not get too brown, but a little caramelization is good. 

In another skillet, heat the other half of the butter and oil over medium high heat. Add the mushrooms and saute quickly, letting them brown a little before turning them. 

Add the mushrooms to the onions along with the thyme and salt. Stir in the heavy cream and grated Swiss cheese. Pour into a gratin dish. Sprinkle with the Parmesan and bake at 400 degrees for 10-15 minutes or until bubbly.