In a medium saucepan, bring the stock and pumpkin puree to a boil over high heat, stirring until combined. Reduce to a simmer.
Meanwhile, in a large saucepan heat the butter or oil over medium heat. Add in the onion and garlic and let soften for 2-3 minutes. Add in the rice and thyme and cook for 2-3 more minutes or until the rice is just translucent on the outsides.
Add in 1-2 ladles of stock into the rice and stir. Let simmer until the liquid has evaporated, stirring occassionaly. Continue adding in ladles of stock, letting the rice simmer until the stock is evaporated and stirring until you have used up all of the stock and the risotto is creamy in texture - 20-25 minutes.
Add in the parmesan cheese and nutmeg and stir until combined. Season to taste with salt and pepper. I usually don't add any salt because the stock and parmesan are salty enough.
Serve immediatly and top with your favorite toppings.