Potato Gratin with Porcini Mushrooms and Mascarpone Cheese Recipe

How to make it

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• Place porcini and 1 cup boiling water in medium bowl.
• Place small bowl atop mushrooms to keep submerged. Let soak 20 minutes.
• Drain and coarsely chop mushrooms.
• Melt butter with oil in medium skillet over medium heat.
• Add mushrooms and sauté until beginning to brown, about 3 minutes.
• Sprinkle with salt and pepper.
• Remove from heat. Whisk 1/4 cup Parmesan and next 4 ingredients in small bowl; season with salt and pepper.
• DO AHEAD: Mushrooms and cheese mixture can be prepared 1 day ahead. Cover separately and chill.
• Preheat oven to 325°F. Butter wide shallow 2-quart baking dish. Arrange 1/4 of potato slices in bottom of dish.
• Sprinkle lightly with salt and pepper. Scatter 1/4 of mushrooms over.
• Repeat. Spread half of cheese mixture over, shaking dish to settle. Repeat with remaining potatoes and mushrooms in 2 layers each; spread remaining cheese mixture over. Sprinkle 2 tablespoons Parmesan over.
• Place gratin dish on rimmed baking sheet.
• Bake gratin until top is brown and sauce is bubbling at edges, about 1 hour 15 minutes.
• Let gratin rest 15 minutes before serving.
• DO AHEAD: Can be made 2 hours ahead. Let stand at room temperature. Tent loosely with foil and rewarm in 300°F oven 20 minutes.
• *Available in the produce section of many supermarkets and at specialty foods stores and Italian markets.
• **Italian cream cheese; sold at many supermarkets and at Italian markets