Defrost the puff pastry slices on a lightly floured work surface. Clean and slice the mushrooms. Cut turkey breast and gorgonzola into cubes. Peel onion and garlic and dice finely. Heat 2 tablespoons of oil in a pan and fry the onion in it until transparent. Add the spinach, let it thaw, season with salt, pepper, garlic and nutmeg and steam briefly.
Remove the spinach from the pan and set aside. Heat 2 tablespoons of oil in the pan and fry the mushrooms. Take them out and let them drip off on a kitchen towel. Mix mushrooms, turkey breast, gorgonzola and spinach. Whisk the egg in a bowl. Brush the edges of the puff pastry slices 1 cm wide with egg and arrange the slices slightly overlapping to form a large square surface. Press the seams lightly together. Lay out the puff pastry in a slightly oiled pie tin (24 cm Ø). Cut off protruding edges of the pastry. Spread the spinach mixture on the dough. Mix 5 eggs and milk and season with salt and pepper. Pour egg mixture over the spinach.
Press the seams lightly together. Lay out the puff pastry in a slightly oiled pie tin (24 cm Ø). Cut off protruding edges of the pastry. Spread the spinach mixture on the dough. Mix 5 eggs and milk and season with salt and pepper. Pour egg mixture over the spinach. Bake the pie in a preheated oven (electric cooker: 200 °C/ gas: level 3) for about 45 minutes. Serve warm