Bake the pumpkin pieces in a 180C oven for 15 minutes and put aside.
Cook the chicken breasts (barbecue, grill, fry pan, poach, oven) until just cooked through and put aside. After chicken has cooled a little, cut into 1 - 2 cm cubes depending on preference. (Alternatively, you can cut into cubes first and then stir-fry).
While doing steps 1 and 2, put the oil in a large saucepan on medium/hot and when heated, put the onions and garlic in and cook until onions begin to get soft - about 5 minutes.
Add the rice and stir until the grains start to swell and burst then reduce heat to low and add the cup of white wine.
Stir over low heat until the liquid has been absorbed.
Add, say, half a cup of the hot stock and keep stirring while the rice absorbs it.
Keep adding stock in this way, stirring constantly.
Just as the final liquid is being absorbed and rice is cooked (about 20 - 25 minutes), add the cooked cubed chicken and pumpkin and gently stir.
Remove from heat, stir in grated parmesan cheese, (add freshly ground black pepper if you like) and serve.