Preheat oven to 350 degrees F.
Peel and seed squash. Score 1 squash with a knife and season with olive oil and salt. Roast in oven until browned and cooked through. Puree in food processor. Dice other squash and saute in a pan in olive oil. Heat rice in a little olive oil. Slowly add stock, 2 ounces at a time, until absorbed. Once rice is fully cooked fold in butter, Parmesan, and mascarpone. Add squash puree, to taste, and fold in the sauteed diced squash. Season and garnish with sorrel.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.