1 pound elbow macaroni
2 C milk
1 C heavy cream
1 C sour cream
8 tablespoons (1 stick) unsalted butter, divided
1/2 cup all-purpose flour
12 ounces gruyere, grated (4 cups)
12 ounces extra-sharp cheddar, grated (4 cups)
3 ounces blue cheese, crumbled (1 cup)
8 baby portabello mushrooms, quartered
1/2 C panko
1 T salt
freshly ground pepper
3 T black truffle oil
Preheat oven to 375 ° F. Drizzle oil into a large pot of boiling water and cook macaroni according to package directions. Drain well.
Meanwhile, heat milk, cream and sour cream briefly in the microwave, but don’t get it to a boil. Melt 6 tablespoons of butter in a large stock pot, and when the butter begins to bubble, add the flour and whisk over low heat for about two minutes. Add the hot milk, cream and sour cream and continue whisking until mixture is smooth. Remove from heat, add the gruyere, blue cheese, half the cheddar, portabellos, salt and whisk until sauce is thickened and smooth. Add the cooked macaroni and stir well.
Pour into a 3-quart baking dish. Melt the remaining 2 tablespoons of butter, combine it with the panko, and sprinkle on top of the macaroni. Bake for 30 to 35 minutes or until the sauce is bubbly. Top with remaining cheddar and let bake for another 5 minutes, or until cheese melts. Remove from the oven, sprinkle with truffle oil and serve.