Boil the quail eggs for 4 to 5 minutes. Cool and peel them. Cut each in half.
Drain the tuna and mix it with mayonnaise, lemon juice, salt, and pepper in a bowl.
Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Cut the puff pastry into small circles or sea shell shapes using a cutter.
Place a spoonful of the tuna mixture onto each pastry cutout and top with a quail egg half.
Cover with another pastry piece and seal the edges firmly using a fork.
Bake for 12 to 14 minutes until puffed and golden.
Let cool slightly and serve warm or chilled.