Brown the minced meat and the onion in a frying pan for about 5 minutes, without adding any oil.
Mix in the garlic, tomatoes, tomato purée, red pepper and oregano then fry for about 2 or 3 minutes. Add 150ml of water and bring to the boil. Put a lid on and stew for about 15 minutes. Sprinkle with salt and pepper.
In the meantime, immerse the lasagna sheets in boiling water or hot stock.
Place the spinach in a colander. Above the sink, tip boiling water over the spinach until wilted. Drain the excess water.
In a bowl, combine the spinach, ricotta and pesto and stir well.
Preheat the oven to 180°C. Lay 2 sheets of lasagna over the bottom of a 2.5-litre ovenproof baking dish. Spoon half of the chicken mixture on top. Cover with half of the spinach mixture then lay 2 more sheets of lasagna and the rest of the chicken mixture, minus a couple of tablespoons.
Top with the rest of the spinach-ricotta mixture. Finish with the last 2 lasagna sheets. Spread over the reserved chicken mixture and then the crème fraîche. Scatter the grated Mozzarella and Parmesan on top.
Put in the oven for about 25 to 30 minutes, until the cheese turn golden and small bubbles start to form.