Tom yum soup with prawns

Name: Tom yum soup with prawns
Prep time: 10 min
Cook time: 30 min
Total time: 40 min
Cuisine: Asian, Thai
Ingredients: 200g onions, roughly chopped; 150g tomatoes, roughly chopped; 20g red chilli, sliced; 15g galangal, peeled and sliced; 2 lemongrass stalks, bashed; 270g whole raw king prawns, peeled and deveined, heads removed and reserved; 1 chicken stock cube; 120g oyster mushrooms, sliced; 8 lime leaves; 5 tsp fish sauce; 5 tsp lime juice; 70ml Thai coconut milk; 1 tbsp Thai chilli jam (optional); small handful of coriander, roughly chopped (optional)