Heat stock in separate saucepan and keep hot for later use.
Sauté the onion in olive oil and half the butter in a large, wide pan over low-medium heat. Reserve half the butter for later. Sauté for 5-8 minutes.
While the onions are sautéing, cut the squash into small cubes.
Add the garlic to the onions and sauté for another minute. Add the squash and rosemary and continue cooking for twenty minutes or until squash is soft and starting to turn creamy. If you are using a drier squash or want the squash as soft as possible, add some stock already.
Remove rosemary sprig.
When the squash is becoming creamy, add the rice and cook for another minute, stirring. Start adding the stock a little bit at a time, stirring constantly. Continue until rice is cooked and all the stock is absorbed. Test and, if rice isn't tender enough, add a bit more stock or water.
Add grated cheese and remaining butter. Add optional ingredients, if desired. Serve immediately.
Servings 4