Cut the pumpkin and apple into cubes, peel the onion and garlic and dice. Mix with coriander, sage, salt, pepper and olive oil, place on a baking sheet and roast in the oven for 35 minutes.
When the pumpkin is soft, put everything in a blender and pour on the vegetable stock. Puree smooth and velvety and place in a saucepan. Bring to the boil again, season with salt.
Serve with the sage leaves, roasted pumpkin seeds and chopped herbs. If you like, you can add toasted bread slices.
The soup will keep in an airtight container for up to 5 days in advance.