Preheat oven to 200 C / Gas mark 6. Place the pumpkin flesh side down on a large baking sheet. Cover with foil and cook on the middle shelf for around 1 hour. Remove from the oven and scoop the flesh off the pumpkin and put to one side.
In a large pan, melt the butter and saute the onions, red chilli and garlic until nice and soft. Add the cooked pumpkin flesh, stock and seasoning.
When the soup mixture is cooked blend using a hand blender until nice and smooth.
Warm the milk in a separate pan, but do not boil. Then stir into the soup gently.
Serve at once or put aside and gently reheat when ready to eat.