This is Harriet’s — my mum’s friend in Finland — a wonderful, stylish lady and cook. I tasted this many years ago and have always remembered it. Her original recipe uses pike-perch fillets, but you can use any fish fillets you like, just make sure they have no bones. In this pie the mash is only around the rim, not covering the whole thing, and it is important to use a dish that is no deeper than 6 cm (2½ inches). Maybe make a few smoked salmon crostini for a starter and serve a green salad and bread with your pie and that really is a complete family dinner, I feel.