1. Preheat the oven to 200°C (400°F).
2. Thaw the spinach over low heat in a saucepan, then remove any excess water (feel free to press it to remove the water!).
3. Crumble the goat cheese log.
4. In a large buttered baking dish, layer lasagna noodles, followed by a layer of spinach, then a layer of goat cheese crumbles, then a little béchamel sauce, then a little salt and pepper, and repeat with another layer of noodles...
5. Coarsely chop them (I do it with scissors).
6. Repeat this process for 2 or 3 layers, finishing with the béchamel sauce and topping with grated gruyère cheese.
7. Bake for about 30 minutes and serve hot with a walnut salad.