6 large portobello mushrooms (about 1 1/2 pounds), stems discarded
3 tablespoons good olive oil
1 tablespoon balsamic vinegar
Kosher salt and freshly ground black pepper
2 1/2 cups good chicken stock, preferably homemade
2 cups half-and-half
3/4 cup fine cornmeal
1/4 cup imported Italian mascarpone cheese
4 ounces Gorgonzola piccante, crumbled