Dr Clare and Justine's Sausage Lasagne - Simply Veg

Ingredients

• 6 good-quality sausages (around 400g total weight)
• 2 medium onions, peeled and finely chopped
• 2 garlic cloves, peeled and finely chopped
• 1 tsp dried oregano
• 1 × 400g can chopped tomatoes
• 250g young spinach leaves
• 2 medium courgettes, trimmed and sliced lengthways into strips 3–4mm thick
• good pinch ground nutmeg
• 200g full-fat crème fraîche
• 40g Parmesan, finely grated