Irish Seafood Chowder

Name: Irish Seafood Chowder
Ingredients: 10 ounces / 300 grams frozen mixed seafood (precooked not raw); 5 ounces / 150 grams frozen whole prawns (shrimp) (raw); 1 pound / 450 grams chopped potato (1 dice) (approximately 2 large potatoes); 2 stalks chopped celery (½ dice); 1 large chopped carrot (½ dice); 7 ounce / 197 gram tinned whole kernel sweetcorn; 1 pint / 480 ml milk ((2 cups)); 1 cup / 240 ml single cream (single cream or pouring cream); 2½ ounce / 75 grams butter; 2 cloves garlic (finely minced); 3 teaspoons cornflour (mixed to a paste with 2 tablespoons water); Salt to taste; Black pepper to taste