500g/1lb 2oz floury potatoes (such as Maris Piper), unpeeled, cut into large chunks
150–175²µ/5½–6´Ç³ú plain flour, plus extra for dusting
1 tsp baking powder
sea salt and freshly ground black pepper
50²µ/1¾´Ç³ú butter, plus extra for frying and to serve
1 free-range egg, beaten