Place the puff pastry slices next to each other and let them thaw for about 10 minutes. In the meantime clean the leek, chop finely, wash and pat dry. Heat the oil in a pan and sauté the leek in it.
Remove from the pan and cool down. Wash the salmon and pat dry. Cut salmon into cubes. Sprinkle with lemon juice and season with salt and pepper. Wash tarragon, dab dry and chop finely.
Dice the cheese. Whisk eggs with milk and season with salt, pepper and nutmeg. Place the puff pastry slices on top of each other and roll out (30 x 40 cm). Cut into 12 squares (10 x 10 cm).
Grease the muffin tin (12 wells). Place a piece of dough in each trough. Mix salmon, leek and tarragon and fill in. Spread egg milk into the muffin forms. Place the diced cheese on top and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes.
Allow to cool slightly in the mould and carefully lift out. Serve with green salad in a vinegar-oil vinaigrette with chives.