Toss the apricot slices with the cornstarch, sugar, almond extract and lemon juice until everything is well combined and there are no lumps of cornstarch left. Set aside for about 15 minutes.
Put the puff pastry sheet on a floured surface and gently roll out to a square.
Cut the pastry into four equally sized squares.
Spoon a little of the stone fruit onto the center of each square. Gently pull one side over into a triangle while gently stretching it over the fruit and then use a fork to press along the edges to seal.
Brush each turnover lightly with the egg wash, and then cut a couple of small slits in the top with a sharp paring knife or poke small holes with a fork.
Bake on a parchment lined baking sheet for about 20 minutes, or until the turnovers are risen and golden brown.
Cool slightly, dust with powdered sugar if you want to, and then enjoy right away.
Hint: Serve with vanilla bean ice cream for an extra treat!