Kuma's Pumpkin Soup

Boil water and add the following ingredients consecutively:

1. already boiled and mashed pumpkin
2. salt, white pepper, chicken stock
3. full cream milk
4. maize flour/corn starch for thickening (not necessarily! added if only it isn't thick enough)
5. small box cut of fresh mushroom
6. butter
7. chicken egg, white part only, beaten, pour after the fire is turned off
8. sliced coriander