Make the compote: combine the water and sugar in a small saucepan over low heat. Stir until the sugar dissolves, then add the rhubarb, cardamom pods, and orange rind. Bring to a boil, then reduce the heat to low and simmer for about 15 minutes, until the rhubarb is soft. Remove from the heat, discard the orange rind and cardamom pods, and set the compote aside to cool completely.

Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a bowl, combine the cooled rhubarb compote with the cubed apple.

On a lightly floured surface, cut the thawed puff pastry sheet into 8 even squares, roughly 4 inches (10cm) each. Divide the apple-rhubarb mixture evenly between 4 of the squares, leaving a small border around the edges.

Using a sharp knife, cut 5 to 6 evenly spaced slits into each of the remaining 4 squares, starting about 1.5 inches (4cm) in from one edge. Carefully lay a cut square on top of each filled base and press the edges together firmly to seal. Trim any uneven edges.

Brush the top of each pie with cream and sprinkle generously with sugar.

Bake for 15 to 20 minutes, until the pastry is puffed and deep golden brown. Let the pies cool for a few minutes on the tray before transferring to a wire rack.