If you prefer the soup to be 100% Vegetarian, you can substitute vegetable stock for the chicken stock. I prefer to serve with toasted sourdough. A swirl of cream will make this look nicer and taste richer.
Place squash cubes & 1 tbsp of butter into a skillet over medium heat. Stir occasionally until cooked through (roughly 10 minutes) then remove from heat & set aside.
Melt remaining butter in a saucepan over medium-high heat. Add onion & garlic; cook & stir for 2 minutes until they begin to soften, then stir in the rice. Continue cooking & stirring until the rice is glossy from the butter, & the onion begins to brown on the edges, about 5 minutes more.
Pour in the white wine; cook, stirring constantly, until it has evaporated. Stir in ⅓ of the hot vegetable stock; reduce heat to medium. Cook & stir until the stock has been absorbed by the rice, 5 to 7 minutes. Add half of the remaining stock, & continue stirring until it has been absorbed.
Finally, pour in the remaining stock & butternut squash, & continue stirring until the risotto is creamy. Stir in the Parmesan cheese, & season to taste with salt & pepper. Finally top each individual serving with Pecorino Romano cheese.