Mushroom and Potato Gratin

Ingredients

• Salt and pepper - To taste
• Fresh thyme - 1 tablespoon, chopped
• Parmesan cheese - 1/2 cup, grated
• Gruyere cheese - 1 cup, grated
• Milk - 2 cups
• All - purpose flour - 1/4 cup
• Butter - 4 tablespoons
• Garlic - 2 cloves, minced
• Onion - 1 medium, thinly sliced
• Mushrooms - 1 pound, sliced
• Potatoes - 2 pounds, thinly sliced

Instructions

1. Preheat the oven to 375°F.
2. In a large skillet, melt the butter over medium heat.
3. Add the sliced mushrooms, onion, and minced garlic. Cook until the mushrooms are golden brown and the onion is soft, about 8-10 minutes.
4. In a separate saucepan, melt 2 tablespoons of butter over medium heat.
5. Whisk in the flour and cook for 1-2 minutes, until lightly golden.
6. Slowly whisk in the milk and continue cooking until the mixture thickens, about 5 minutes.
7. Stir in the grated Gruyere cheese and half of the grated Parmesan cheese until melted and smooth.
8. Season with salt, pepper, and fresh thyme.
9. Layer half of the sliced potatoes in a greased baking dish.
10. Spread half of the mushroom mixture over the potatoes.
11. Pour half of the cheese sauce over the mushrooms.
12. Repeat the layers with the remaining potatoes, mushrooms, and cheese sauce.
13. Sprinkle the remaining Parmesan cheese on top.
14. Cover the baking dish with foil and bake for 30 minutes.
15. Remove the foil and bake for an additional 15 minutes, or until the top is golden and bubbly.
16. Let the gratin cool for a few minutes before serving.