Bring the stock to a bare simmer in a 2-quart / 1.9 L saucepan and keep it on low heat. While it warms, dice the onion, mince the garlic, grate the Parmesan and chop 6 of the sage leaves.

Melt 2 tbsp butter with the olive oil in a 28 cm / 11-inch deep sauté pan over medium heat. Add the 12 whole sage leaves and fry for 45 to 60 seconds until they turn deep green and stiff. Lift them onto paper towel and sprinkle with a pinch of salt.

Add the onion and 1/2 tsp salt to the sage butter. Cook for 5 to 6 minutes, stirring, until soft and translucent without browning. Stir in the garlic and chopped sage for 30 seconds, then add the rice and stir for 2 minutes until the edges turn translucent and smell nutty.

Pour in the wine and stir until it's absorbed, about 2 minutes. Stir in the pumpkin purée, smoked paprika, nutmeg, cinnamon and pepper, and cook for 1 minute so the purée loses its raw canned edge.

Turn the heat to medium-low and add the hot stock about 120 ml (1/2 cup) at a time, stirring often and waiting until the pan looks nearly dry before the next ladle. Expect about 9 additions over 18 to 20 minutes. Taste at 18 minutes: the rice should be tender with a slight bite in the center, and the risotto should flow slowly when you drag a spoon across the bottom. If the stock runs out first, use hot water.

Take the pan off the heat. Stir in the remaining 2 tbsp cold butter, most of the Parmesan and the lemon juice, then taste and add salt if needed. Loosen with a splash of hot stock if it looks tight. Spoon into warm bowls and serve within 5 minutes, topped with the crisp sage and the reserved Parmesan.