Thai style pumpkin soup

I had this tasty and moreish soup recently at a vegetarian cafe and I fell completely in love, I couldn't get enough of it and knew that I had to try it again! You can use dried/jar spices, but I would strongly recommend using fresh ginger, lemongrass and turmeric where possible as it will give you the best flavour. 

1 litre vegetable stock
3 cups peeled and cubed pumpkin (butternut or kent is recommended)
1/2 an onion, chopped roughly
1 thumb-sized piece of turmeric
1 thumb-sized piece of fresh ginger
3 tsp finely chopped lemon grass
3 sprigs fresh coriander 
3 cloves garlic
1.5 tsp palm sugar
3 kaffir lime leaves, finely sliced / 1 tsp grated lime rind 
1 red or green chilli, seeded
1 tsp fish sauce
1/2 tsp cumin
Juice of half a lime
200ml coconut milk 
Small bunch (4 leaves per serve) of baby spinach to serve 
1 tbspn coconut yoghurt to serve (available at health food stores)

1. Place stock in a large saucepan and bring to the boil
2. Add the pumpkin, onion and the leftover stalk of the lemongrass, add a couple of coriander stalks too if you have them leftover (the stalks, especially at the root end, have the most flavour)
3. Boil for 5 minutes then turn down to a light simmer
4. While the pumpkin/stock is cooking, make your spice paste. 

Spice paste :
5. Place turmeric, ginger, lemon grass, coriander, garlic, lime leaves/zest, and chilli in mortar and pestle and grind to a paste (or pulse in blender/food processor)

6. Turn pot down to low heat and add spice paste gradually into the pot, stirring after each addition. Stir in the cumin, fish sauce and lime juice. 
7. Place lid on the pot, raise the heat and bring to the boil, then lower to a simmer and cook for 15-20 minutes or until the pumpkin is soft
8.  Remove the pot from the heat, scoop out the onion if you are intolerant like me, and add in coconut milk, add it gradually to your own taste, I used about 150mls.
9. Taste the soup and adjust flavours if needed 
10. Allow to cool for 10-15 minutes then blend with stick blender, food processor or blender. 
11. Push through a sieve so there is no stringy bits of lemongrass etc in there
12. Serve hot with a dollop of coconut yoghurt and spinach (spinach will wilt when you add to soup bowl).