Bring 1 quart stock plus 1 cup water to a simmer in a sauce pot then reduce heat to low.
Heat a medium skillet over medium to medium-high heat with extra-virgin olive oil. When oil ripples, add the onions and garlic and soften 2 to 3 minutes. Add rice and toast 2 to 3 minutes more. Add wine and cook it out completely, stirring occasionally, 2 to 3 minutes. Ladle in stock in intervals, a couple of ladles at a time. Allow liquids to evaporate each time. Risotto will cook 18 minutes, total, from the first addition of liquid. Defrost the squash in the microwave in a dish to collect any liquids. Stir the squash into the rice the last 3 minutes of cook time. Season with nutmeg and salt and pepper, to taste. In the last minute of cooking time, stir in the butter in small pieces, sage and cheese, serve.