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: In the absence of fresh sage, do not substitute dried. As a substitute, 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

Note: You may garnish with fresh Italian parsley, but do not cook the parsley in the pasta.