Iggy's Conchiglie al Forno with Mushrooms and Radicchio

Ingredients:
6 ounces shiitake mushrooms, cleaned and trimmed
8 T (1 stick) unsalted butter
1 teaspoon kosher salt
2 cups (2 medium heads) finely shredded radicchio
2 1/2 cups heavy cream
1/2 cup freshly grated parmigiano-reggiano (1 1/2 ounces)
1/2 cup coarsely shredded fontina (1 1/2 ounces)
1/2 cup crumbled gorgonzola (3 ounces)
2 teaspoons ricotta
6 leaves fresh sage, chopped
1 pound imported conchiglie rigate (pasta shells)

Preparing the pasta:
Preheat the oven to 500 degrees F.

Bring 5 quarts of salted water to a boil in a stockpot.

Remove the stems from the mushrooms and reserve for another use. Slice the mushroom caps about 1/4-inch thick. Heat 6 tablespoons of butter in a large skillet; add the mushrooms and 1/4 teaspoon salt. Saute over medium heat, stirring frequently, until they are cooked through, 3 to 5 minutes.

In a large mixing bowl, combine the mushrooms, radicchio, cream, cheeses, sage, and remaining salt.

Parboil the pasta shells for 4 minutes; drain and add to the ingredients in the mixing bowl. Toss to combine.

Divide the pasta mixture among 6 to 8 individual, shallow, ceramic gratin dishes (1 1/2 to 2 cup capacity). Dot with the remaining 2 tablespoons of butter and bake until bubbly and brown on top, about 7 to 10 minutes.

Note: If fresh sage isn't available, do not substitute dried. Instead, choose one of the following: 1 tablespoon coarsely chopped fresh tarragon OR 1 teaspoon fresh thyme leaves OR 8 leaves fresh rosemary OR 1/4 teaspoon fennel seed