Place the sultanas in a bowl of water to hydrate them.
Peel and slice the garlic cloves and fry on a low heat in a frying pan with a drizzle of olive oil.
Wash and drain the spinach and add to the frying pan. Increase to a medium heat and place a lid on the frying pan. Stir and sauté the spinach until it reduces.
Add the drained sultanas to the frying pan with the spinach, remove from the heat and leave to rest.
Heat the milk in a bowl in the microwave.
Melt the butter in a saucepan and add the sieved flour. Stir with a balloon whisk on a medium heat.
Gradually add the milk to the saucepan while you whisk constantly for a few minutes until you get a lump-free bechamel sauce. Add the salt and nutmeg.
Add half of the bechamel to the frying pan with the spinach, stir and mix. Reserve the rest of the bechamel.
Place 4 lasagne sheets into the base of a mould and cover with a layer of the filling. Continue placing sheets and filling until you form several layers.
Add the remaining bechamel sauce onto the top layer and cover with grated cheese.