Thaw the spinach leaves, squeeze out well (important, otherwise the sauce will be too watery), finely chop the garlic. Sauté the spinach with garlic and white wine in 1 tablespoon butter until just barely done, season with salt and pepper. (You can omit the butter when preparing in the microwave).
Put in a buttered baking dish. Place the lightly salted plaice fillets on top, drizzled with the juice of half a lemon. Spread the crabs over it.
For the sauce, finely chop the onion and sauté in 1 tablespoon butter until translucent, add the thyme and pour the milk on top. Bring to the boil briefly and let steep for 5 minutes.
Melt 1 tablespoon butter, add flour and sweat while stirring. First add the thyme milk in 2 to 3 servings, always stirring so that there are no lumps. Pour in the cream and cook for about 10 minutes on low heat while stirring. Add the parmesan and, if necessary, grated cheese, allow the cheese to melt, remove the saucepan from the heat, stir in 2 egg yolks, season with salt, pepper, nutmeg and, if you like, with granulated broth.
Pour over the casserole.
If you like, you can also put flakes of butter on it.
Bake in the preheated oven top / bottom heat at 200 ° for 12-15 minutes.
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