PRAWN, SPINACH & PASTA BAKE WITH WALNUT TOPPING

Pre-heat oven to 190°C (370°F). Boil the pasta until al dente, then drain and put aside.
Gently fry the leeks, mushrooms and prawns in oil until just tender (don’t overcook them as they will cook further in the oven). Put aside.
Meanwhile, put the butter into a big, heavy saucepan on high heat. At the point it’s melted, toss in the flour and quickly stir in. When it’s just combined with no lumps, pour in a little of the milk (about half a cup). Stir vigorously until it becomes smooth, add more milk, stir till smooth, and so on.
Turn down the heat to low. Now add the mustard and nutmeg, and salt and pepper to season. Cook for 2 mins more, stirring constantly.
Remove from the heat and stir in two-thirds of the cheese, plus the extra parmesan. Taste test to see if it’s seasoned well and adjust seasoning if necessary. Add the spinach, the leeks and prawns, as well as the cooked pasta. If the mixture’s too thick, add a little extra milk to loosen it.
Put the mixture into two ovenproof dishes (if you’re cooking it all now) and scatter the remaining cheese and chopped walnuts over top. Bake for 40 mins until golden brown and bubbling. You could make this ahead as it freezes well (and tastes even better once frozen!).