Place the Fish Fingers on a baking tray and bake until crispy and golden.
Meanwhile heat half the butter in a saucepan until foaming. Add the carrots and cook for around 5 minutes, then add the leeks and continue cooking until soft.
Add the rest of the butter and flour and cook out for a minute or so until smelling biscuity.
Pour in the milk gradually, beating it in with a wooden spoon, until you have a thick sauce. Bring to a simmer and cook for a few minutes then add most of the parmesan.
Use a little oil to grease a medium sized baking dish and add a layer of the sauce. Place the first layer of lasagne sheets on top.
Top with another layer of the sauce, half the fish fingers, spinach, peas. Top with lasagne sheets and repeat again, topping with a final layer of lasagne sheets, sauce and sprinkling of parmesan.
Bake for around 30 minutes until golden and bubbling.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2019/08/03/birds-eye-fish-finger-lasagne/