Bring 200 mililiters of water to a boil in a small saucepan, stir through, remove from the stove. Stir the flour in a cup with a tbsp of water, making sure it does not clump. Add flour-water mixture to small saucepan, stir well, place repeatedly on kitchen stove, stir with whisk until sauce repeatedly comes to a boil and thickens.
Fold in crème fraîche, add Metaxa, season with nutmeg and a little salt (because the gyros is already seasoned).
The sauce is used for gratinating gyros. The above mixture is enough for a commercial unit that you get from the Greek snack bar (without tzatziki, but with onions). Put the gyros in a gratin dish and pour the sauce over it.
Next, bake in the microwave (ten minutes at 600 watts) or in the oven (preheated, 15 minutes at 200 °C ). If desired, the gyros casserole can be topped with feta cheese.