In a mixing bowl, combine flour, sugar, and salt. Cut in cold butter until the mixture resembles coarse crumbs. Gradually add ice water until a cohesive dough forms. Wrap in plastic wrap and chill for at least 30 minutes.

Heat milk in a saucepan until simmering. Whisk egg yolks and sugar in a bowl until pale. Add cornstarch and mix well. Slowly pour hot milk into egg mixture while whisking. Return to saucepan and cook, whisking until thickened. Stir in cardamom and cool completely.

Preheat oven to 400°F (200°C). Roll out chilled dough into a 12-inch circle. Transfer to parchment-lined baking sheet. Spread cooled cardamom pastry cream in the center, leaving a 2-inch border. Arrange sliced apricots on top.

Sprinkle additional sugar over apricots. Fold edges of dough over filling, pleating for a rustic look. Bake for 30-35 minutes, until crust is golden and apricots are bubbly.

Remove from oven and cool on baking sheet for 10-15 minutes. Serve warm or at room temperature, optionally with whipped cream or vanilla ice cream.