Quick and simple creamy seafood chowder soup

Name: Quick and simple creamy seafood chowder soup
Ingredients: 50 gram butter; 1 leek, finely chopped (white part only); 3 clove garlic, finely chopped; 2 level tbsp plain flour; 2 1/2 cup milk; 2 1/2 cup fish or chicken stock; 1/2 cup cream; handful shellfish in shells (eg mussels or clams) scrubbed and cleaned – optional; 250 gram raw fish eg monkfish, snapper, tarakihi, hapuku, cut into 3-4cm chunks; 250 gram raw prawns (and/or scallops); 200 gram smoked fish or salmon, flaked; juice ½ lemon; 1/4 cup finely chopped parsley; 1/4 cup chopped chives, to serve