Preheat the grill to high. Line 2 baking trays with foil and arrange the sausages in the trays. Grill, turning frequently, until cooked through. When cool enough to handle, cut into chunks. Set aside and turn the oven to 200ºC, fan 180ºC, gas 6.
Meanwhile, cook the pasta according to the pack instructions until al dente. Drain well.
In a large bowl, combine the tomatoes with the crème fraîche. In another larger bowl, mix half of this tomato sauce with all the pasta, spinach and sausages.
Divide the mixture between 2 x 2-litre ovenproof dishes, then pour the remaining tomato sauce over each. Top each with 25g grated cheese.
To eat, bake for 20 mins, then serve. To freeze: allow to cool, unbaked, cover with clingfilm, then foil, and freeze for up to 3 months. To eat, remove from the freezer, defrost in the fridge and bake as instructed above.