1. Heat your oven to 200C/Gas Mark 6.
2. Heat the olive oil in large saucepan or stockpot and fry the garlic for half a minute. Put the spinach in the pan, add some salt and pepper, toss the spinach leaves in the oil, turn down the heat to low and cover for 2 minutes. The spinach should then be wilted.
3. Remove the spinach from the pan and put to one side in a bowl. Once it has cooled, squeeze out any excess water.
4. In a separate pan, melt the butter. Once it starts to bubble, add the flour and stir to form the base for a béchamel sauce. Gradually pour in the milk and whisk until you have a thick, white sauce then turn off the heat. Stir in the nutmeg and mustard along with some seasoning and then add half the mozzarella. Stir until all combined.
5. In a separate bowl, combine the ricotta, parmesan, cooked spinach and approximately one third of the béchamel sauce. Add further seasoning if required.
6. Heat a small non-stick frying pan and gently toast the pine nuts for a minute or two until they start to brown. Remove from the heat.
7. To assemble to lasagne, put a quarter of the ricotta mix in the bottom of a baking dish and spread until covered. Drizzle a small amount of the béchamel sauce on top, then a few pine nuts, and cover with one layer of lasagne. Repeat this process until you’re left with enough béchamel sauce to cover the surface, then top with the remaining mozzarella.
8. Bake in the oven for 30 minutes, or until the lasagne sheets are cooked through and the top is golden brown.