Chop the onion finely and mince the garlic. If using fresh pumpkin, roast it until tender, then blend until smooth to create a puree.
Heat a splash of olive oil and a tablespoon of butter in a wide pan over medium heat until shimmering. Add the chopped onion and cook until translucent and fragrant, about 5 minutes.
Add the arborio rice to the pan and toast, stirring constantly, until the edges become slightly translucent, about 2 minutes. You should hear a gentle sizzle.
Pour in the white wine and stir until mostly absorbed, releasing a sweet aroma as it cooks off, about 1-2 minutes.
Begin adding the warm vegetable stock, about half a cup at a time, stirring gently and continuously. Wait for the rice to absorb most of the liquid before adding more. Continue this process, stirring regularly, until the rice is halfway cooked and creamy, approximately 10 minutes.
Stir in the pumpkin puree, mixing well to incorporate the vibrant color and sweetness. Cook for another 10 minutes, adding more stock as needed, until the rice is tender but still has a slight bite.
Add the remaining tablespoon of butter and the grated Parmesan cheese. Stir until the risotto becomes glossy and silky, about 2 minutes. Taste and adjust seasoning if needed.
Remove from heat and let the risotto rest for 2 minutes. The mixture will thicken slightly and become more flavorful.
Serve the pumpkin risotto hot, garnished with fresh herbs like sage or thyme for a fragrant finishing touch. Enjoy the creamy, hearty dish with a comforting aroma and vibrant color.