Melting middle smoked haddock and prawn fishcakes

Name: Melting middle smoked haddock and prawn fishcakes
Cook time: 1 h 20 min
Total time: 1 h 20 min
Cuisine: European, British
Ingredients: 750g floury potatoes, peeled and cut into large even-sized chunks; 15g unsalted butter, plus extra for greasing; 600g undyed skinless smoked haddock; 2 bay leaves; 1 x 200g pack MSC cooked peeled prawns, dried on kitchen paper; 1⁄2 x 25g pack chives, finely chopped; 1 tbsp wholegrain mustard; 125g mature cheddar; 2 medium eggs, beaten; 125g panko breadcrumbs; 3 tbsp vegetable oil, for frying