Cut the pumpkin into large chunks. Place them into a baking tray. Pour some water onto the tray - so the entire bottom is covered. Roast in the oven for 30-40 minutes in 350°F (180°C) until soft (check with fork).
Remove from oven, wait for the pumpkin to cool. Don't pour the water out, as we will need it later. Carefully remove the skin.
Blend the pumpkin pieces together with the water we've kept from before.
In a deep cooking pan mix together a cup and a half of the pumpkin juice, as well as the rest of the ingredients.
Bring the pan to boil, then reduce the heat. Simmer for 20 minutes stirring occasionally.
Chill to serve. Decorate with cinnamon sticks or orange slices.
A 4 pound fresh pumpkin makes around 3-3.5 cups of cooked purée. If you won't use it all for the pumpkin juice - just eat it.