Time: 1 hour 15 minutes
100g of unsalted butter, plus extra for greasing
100g of plain flour
950ml of whole milk
1 tbsp of Dijon mustard
1/2 tsp grated nutmeg
1/2 leek, cut into thin strips
400g of baby spinach
2 garlic cloves, crushed
10 fresh lasagne sheets
500g of cold smoked trout, cut into 2cm squares
250g of cheddar, grated
50g of Parmesan, grated
4 sprigs of dill, chopped
Salad leaves, to serve
Melt 75g of the butter in a heavy-based saucepan over a medium heat. Add the flour and cook out for 1–2 minutes, then slowly add the milk, stirring as you go. Cook for 8–10 minutes, stirring continuously without letting the sauce boil too hard, until thickened. Once thickened, add the mustard and nutmeg.
Preheat the oven to 180°C/Gas mark 4 and grease a lasagne dish with butter.
Melt the remaining 25g of butter in a saucepan, add the leek and cook for 2–3 minutes to soften a little. Season with salt and pepper, then add the spinach leaves (a handful at a time is easier) and the garlic and cook for a further 2–3 minutes, until the spinach has wilted. Drain off the excess liquid.
Spread some of the sauce over the bottom of the dish and place a layer of lasagne sheets on top. Top with some of the leek and spinach mixture, then some cold smoked trout. Sprinkle over some cheddar and Parmesan. Repeat the process, finishing the top layer with sauce, a few pieces of trout, and grated cheese. Bake for 45 minutes, until golden and the lasagne is tender. To check if the lasagne is cooked, insert a fork – if there’s no resistance, it’s ready.
Sprinkle the dill over the top and serve with a fresh green salad.