Finely shred or pulse the pineapple without turning it into a completely smooth purée. Combine it with the sugar, cinnamon stick, cloves, and optional star anise in a wide saucepan, then cook uncovered over medium heat until most of the liquid has evaporated.

Reduce the heat and continue cooking the pineapple mixture for approximately 45–60 minutes, stirring frequently, until thick, sticky, and able to hold its shape when stirred. Add the optional citrus juice, remove the spices, and cool the jam completely before refrigerating it until firm.

Beat the softened butter and icing sugar just until smooth and creamy, then mix in the egg yolks. Sift in the flour, cornstarch, milk powder, and salt, mixing only until a soft dough forms; wrap and chill for about 30 minutes.

Shape the chilled jam into roughly 8–10 g balls and divide the dough into approximately 12–14 g pieces. Flatten each dough piece, place jam in the center, and enclose it completely before rolling into a ball or shaping into a small oval.

Arrange the filled pastries on a parchment-lined baking sheet. Mix the egg yolk with milk or water, brush the tarts lightly, and add decorative lines with a small knife or fork if desired.

Heat the oven to 170°C conventional or 160°C fan/convection. Bake for 18–22 minutes per tray, until the edges are lightly golden and the bottoms are set.

Let the tarts cool on the baking sheet for several minutes before moving them to a rack. The pastry firms as it cools, so wait until they are no longer fragile before storing or serving.