Tuscan lasagne with Italian sausage and caccio e pepe

Ingredients

• 1 packet De Cecco Lasagne sheets
• 1 tbsp olive oil
• 800g sweet Italian sausage, removed from its casing
• 1 cup diced Spanish onion
• 3 garlic cloves, minced
• 2 tbsp tomato paste
• 4 springs thyme
• 450g crushed San Marzano tomatoes
• 2 bay leaves
• 400g fresh ricotta, drained in colander
• 1 cup pecorino, grated
• 2 tbsp flat leaf parsley
• 250ml double/whipping cream cream
• 250ml chicken stock
• ¾ cup Parmigiano Reggiano, grated