Preheat the oven to 190°C.
Heat oil in a large non-stick frying pan and brown the sausage meat over high heat while breaking it up.
Add chili, garlic, and mushrooms and fry for several minutes.
Stir in the crème fraîche and spinach, boil for two minutes, and season.
Mix the tomatoes, tomato paste, sugar, and thyme in a jug and season well.
Spread one third of the ragu sauce into the bottom of an oven-proof dish.
Layer one third of the tomato sauce and half the pasta sheets, then repeat layers twice more.
Sprinkle the grated cheddar cheese over the top.
Bake for 20 to 30 minutes until golden brown and the pasta is tender.