Preheat oven to 425°F. Lightly coat the squash with EVOO; season with nutmeg, salt and pepper. Roast until tender and browned at the edges, 18-22 minutes.
Melt the butter in a small pot over medium heat until it foams. Increase the heat a touch and add the sage leaves. Cook until crisp, then transfer sage to paper towels with a slotted spoon to drain. Chop sage leaves. Reserve brown butter.
Combine the ground veal and beef with the chopped sage and garlic. Season with salt and pepper. Mix in the Parmigiano-Reggiano and form patties.