Roughly chop the spinach, discarding stalks. Stuff it into a large saucepan with 250 ml of water and jam on the lid. Bring to the boil and cook gently for 5 minutes until it wilts to a glossy green mass. Remove, drain and cool. When cool, squeeze the spinach in your hands to wring out excess water. Chop finely and set aside.
Slice the cheese finely and set aside. Heat a non-stick frying pan for 1 minute over a moderate heat. Lay out 4 tortillas and spread each one with a quarter of the spinach, right to the edges. Arrange slices of cheese over the top and scatter with salt and pepper. Top with another tortilla.
Place one tortilla sandwich in the hot pan and dry-fry for 2 – 3 minutes until the cheese just starts to soften. Turn carefully and fry on the other side. Slide out of the pan onto a plate and keep warm while you make the remaining sandwiches. Cut each one into six wedges and serve.