Pre-heat the oven to 200ºC/180ºC fan/ gas mark 6.
Wash the spinach. Cook the spinach in a pan on a low heat until wilted (you might need to do this in batches). If using frozen spinach, cook until defrosted and most of the water has evaporated.
Transfer the wilted spinach to a colander over the sink and allow to cool slightly.
Whilst the spinach is cooling, use the same pan to fry the onion and garlic in the rapeseed oil, until softened.
Add the passata, chopped tomatoes, balsamic vinegar and season to taste. Bring to the boil then reduce the heat and continue to cook for 10 minutes, adding a splash of water if it gets too thick.
Add the Italian herbs and continue to cook for a few more minutes.
Place the cooked peas (as per pack instructions) in the food processor along with the ricotta and some seasoning, then blitz until smooth. It should have a nice, spreadable consistency. If it’s too thick, add a splash of water and blitz again.
Assemble the lasagne: pour one fifth of the tomato sauce into the bottom of an oven-proof dish and spread evenly, cover with three or four lasagne sheets, then spread over one quarter of the ricotta mixture. Repeat the same process until you have used all the lasagne sheets, ricotta mixture and tomato sauce.
Whilst the tomato sauce is cooking, use your hands to squeeze any excess water out of the spinach, then place the drained spinach into a food processor.
Break up the mozzarella ball into small pieces and scatter over the top of the lasagne, along with the grated parmesan.
Place in the oven for 25-30 minutes until the lasagne is golden on top.
Cook the Birds Eye Country Veg Mix according to pack instructions, then serve on the side with a portion of lasagne.