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