Bring stock to a simmer in a large stock pot.

In a large heavy skillet, heat 1 tablespoon over the butter, plus olive oil, over over medium heat. Stir in the onion and sauté until fragrant.

Add the sausage and garlic and cook, stirring, for 2-3 minutes, until the sausage begins to brown slightly.

Add the rice and stir to coat with the butter and olive oil. Stir in the wine and one ladle of the stock. Stir until the liquid is almost absorbed. Add the squash and another 2 ladles of stock. Cook, stirring, until almost absorbed. Continue adding stock and stirring until the rice is plump and tender, about 15-20 minutes.

Add the thyme and season to taste with salt and pepper. Remove from the heat and stir in the remaining tablespoon of butter. Garnish with Parmesan.