Preheat the oven to 200C (180C fan) / 400F.
Line a large roasting tin with non-stick baking paper. Tip the squash cubes into the tin, drizzle with 1 TBSP oil and stir through until the squash is fully coated. Roast for 30 minutes or so, stirring half way through the cooking time.
Meanwhile, gently heat 1 TBSP vegan butter in a large saucepan. Cook the diced onion for a couple of minutes, until it starts to soften. Stir in the garlic and continue cooking for another minute.
Add the risotto rice to the saucepan and stir through to coat the rice in the butter. Add the stock and miso, stir through and bring to the boil. Reduce the heat to low, cover with a lid, and gently simmer for 15 minutes. Remove the lid and stir the rice. Leave on low heat for another couple of minutes or so, until the rice is cooked through but firm to the bite and the excess liquid has evaporated.
When the squash is soft and starting to brown on the outside, remove from the oven. Mash half of it with a fork and stir into the risotto. Stir in the remaining squash cubes. Season with salt, to taste.
Divide the risotto between four warm bowls. Add some dollops of watercress pesto, a sprinkling of toasted pumpkin seeds, some freshly ground black pepper and a few watercress leaves for garnish. You may not use all the pesto, but I recommend placing it in a pot on the dining table, as I’m sure people will want to go back for seconds!