Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper.

Unroll the thawed puff pastry sheet onto a lightly floured surface. Using a 3-inch round cookie cutter, cut out 12 circles. Gently press each circle into the wells of a standard 12-cup muffin tin, establishing a small 'cup' shape.

In a small bowl, combine the apricot preserves, heavy cream, and almond extract. Mix until smooth. Spoon about 1 1/2 teaspoons of the apricot mixture into the center of each puff pastry cup.

In another small bowl, whisk together the egg yolk and water to create an egg wash. Lightly brush the exposed edges of the pastry cups with the egg wash. Sprinkle the sliced almonds over the top of the apricot filling.

Bake for 12 to 15 minutes, or until the pastry is golden brown and puffed around the edges, and the filling is lightly bubbling.

Carefully remove the tarts from the muffin tin using a small offset spatula or butter knife. Let cool on a wire rack for at least 10 minutes before serving.