Preheat the oven to 375°F/190°C/Gas 5.

Use a sharp knife to remove the top from the pumpkin in one piece and set it aside. Remove the seeds and stringy pulp from inside the pumpkin using a spoon or scoop. Replace the lid on the pumpkin. Place on a parchment-lined baking sheet. Bake for approximately 45 minutes until slightly softened. (time will depend on the actual size of the pumpkin). Remove from heat, carefully remove the lid, and set aside to cool slightly.

While the pumpkin is roasting, toast the walnuts in a dry skillet over medium heat for 5-6 minutes. Stir often and watch carefully to prevent burning. Remove from the heat and set aside.

Add oil to a large deep skillet and add the onion. Cook, stirring occasionally, until onions become slightly soft and translucent. Add the diced chicken and sauté until golden brown. Add garlic, tomato puree, and water. Cover the skillet with a lid and simmer over low heat for approximately 20 minutes.

Ladle the filling into the pumpkin. Add chopped walnuts, herbs, cherry tomatoes, and chili pepper if using (reserving some for garnish) and season with salt and pepper to taste.

Return the filled pumpkin to the oven and roast for another 20-25 minutes.

Remove pumpkin from the oven, and garnish with reserved walnuts, herbs, and tomatoes. Serve warm, and enjoy!