Step 1 Preheat oven to 200°C. Line a large baking tray with baking paper. Place pumpkin pieces on prepared tray; drizzle with half of the olive oil. Bake for 20 minutes, or until pumpkin is just tender. Cover to keep warm; set aside.
Step 2 Meanwhile, add vegetable stock and 2 cups cold water to a large saucepan set over high heat. Cover pan and bring to the boil. Reduce heat to low; keep stock water at a simmer.
Step 3 Heat remaining olive oil in a separate large saucepan set over medium heat. Add onion; cook, stirring, for 5 minutes, or until soft. Add rice; cook, stirring, for 1 minute, or until well coated and slightly toasted.
Step 4 Add 1/3 cup of the hot stock water to rice mixture; stir until rice absorbs stock. Repeat process for about 20 minutes, or until rice is tender and creamy, reserving 1/3 cup of the stock water.
Step 5 Add frozen peas, parmesan and reserved 1/3 cup stock water to rice mixture. Cook, stirring, for 3 minutes, or until vegies are just tender; remove risotto from heat. Shred half of the mint leaves and stir into risotto with two-thirds of the cooked pumpkin.
Step 6 Top risotto with remaining pumpkin and mint. Season with cracked black pepper and serve.