Preheat the oven to 190 °C.
Finely chop the sweet onion and garlic and cut the pumpkin into cubes.
Place half of the pumpkin pieces on the baking sheet and sprinkle with pepper, salt, and 2 tablespoons of olive oil. Roast for 25 minutes in the oven at 190 °C.
Add 2 tablespoons of olive oil and the rice to a cast-iron pot. Sauté for 2 minutes until the rice is nice and glossy. Add the onion and garlic. Sauté for 4 minutes and deglaze with sherry. Let it evaporate and add the other half of your pumpkin.
Now add 2 ladles of broth at a time and stir until fully absorbed. After 20 minutes, your rice will be cooked and the broth will have evaporated. Add the Parmesan cheese and mascarpone. Taste and season with pepper and salt. Grate some zest from the lemon over it and add the juice of the half lemon.
Distribute the roasted pumpkin, blue cheese, and watercress over it and serve at the table.
For Grace, I first serve a portion before adding the blue cheese. Blue cheese can be quite strong for the little ones. Pumpkin is her favorite!