Heat the oil in a large deep pan. Place the chicken breasts in and season with salt. Cook on both sides until golden and cooked through. Set aside and slice up.
Place the garlic in the pan (and a little extra oil if necessary). Cook out for 1 minute. Add the tomatoes and cook down until thick then add the stock and simmer for 5 minutes.
Now add the spinach, cream, herbs, salt and pepper. Stir and cook gently until thick and creamy. Set aside and stir in the parmesan.
Take your lasagna dish and spread some sauce on the bottom, followed by 4 lasagna sheets, some chicken, more sauce and 1/3 of the mozzarella. Repeat then top the final layer of sheets with the remaining mozzarella, sauce and parmesan. Cover with foil and bake for 25 minutes.
After 25 minutes remove the foil and cook for a further 20 minutes until the lasagna sheets are cooked and the top is golden brown.