Cover the spinach and 100 ml of water and heat over medium heat for about 16 minutes. Then bring to the boil briefly, stirring several times. Pour into a sieve and drain well. Peel and chop onions and garlic.
Heat 2 tablespoons of oil in a frying pan, crumble the minced meat into it and fry vigorously while turning. Add onions and garlic and fry briefly. Season with salt and pepper. Dice the feta cheese. Mix spinach into the minced meat mixture.
Season again with salt, pepper and nutmeg. Carefully mix in the cheese. Place the pan on a grid and let it cool down a little. Whisk egg and milk. Let the dough sheets rest for about 10 minutes at room temperature.
Spread a slightly moistened tea towel on the work surface, place a dry one on top. Unroll the dough sheets and cover them again and again during preparation to prevent the dough sheets from drying out.
Grease a springform pan (26 cm Ø). Place 5 pastry sheets one after the other in the form, leaving them standing up at the edges. Brush each sheet with 1/2 tsp. oil. Sprinkle the base with breadcrumbs and place the chopped spinach mixture on top.
Drizzle egg milk over it. Place the rest of the pastry sheets on top one by one and brush each with 1/2 tsp. oil. Fold the protruding dough towards the middle. Sprinkle with sesame seeds. Bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) on the lowest rack for 35-40 minutes.
Remove from the oven and arrange on a plate. Yoghurt tastes good with it.