A simple combination to make this cheesy goodness.
This potato gratin recipe will be the talk of the table. Place the dried porcini in a measuring cup and pour on 1 1/2 cups boiling water, let soak for thirty minutes. Line a strainer with a cheesecloth and place over a bowl. Drain mushrooms, collecting the broth in the bowl, then squeeze in cheesecloth to extract juices. Rinse several times and chop medium-fine. Measure out one cup of broth and set aside. Pre-heat oven to 375° F.
Rub inside of a 3 quart baking dish all over with the cut half garlic clove and lightly oil with olive oil. Heat oil in a wide, heavy nonstick skillet over medium heat. Add onion or shallots and cook gently until just tender, roughly 3 to 5 minutes. Turn up heat to high and add mushrooms. Cook, stirring, until they begin to sweat, 2-3 minutes, reduce heat to medium, and add minced garlic, roasting mix, and porcini. Sauté until fragrant, about 30 seconds, then season mushrooms with salt and pepper and cook for another 5 minutes. Add wine and cook, stirring until it is no longer visible in the pan. Taste and adjust seasoning.
Add potatoes and half the cheese to the pan and fold. Arrange in an even layer in baking dish and pour milk over. Combine milk and mushroom broth, season with salt and pepper, and pour over potatoes. Press the veggies down into the milk and bake one hour. After 30 minutes press the veggies down into the milk again. After baking for an hour, remove and sprinkle remaining cheese on top and bake for another 30 minutes until top is golden and the sides are crusty. Remove and let sit for 10 minutes before serving. Enjoy!