Melt 2 tablespoons (28 g) butter in a large skillet over medium heat. Add the apples, brown sugar, apple pie spice, and salt. Cook, stirring occasionally, for 5 to 7 minutes, until the apples begin to soften but still have some firmness in the centers.
2 tbsps (28 g) unsalted butter, 1 lb (454 g) Granny Smith apples, ⅓ cup (71 g) packed light brown sugar, 1½ tsps (3 g) apple pie spice, ¼ tsp (1 g) kosher salt
Whisk the cornstarch and cold water together in a small bowl until completely smooth. Stir the slurry into the apples and cook, stirring constantly, for about 1 minute, until the released apple juices have thickened and no loose liquid remains in the skillet.
1 tbsp (8 g) cornstarch, 2 tbsps (30 ml) cold water
Remove the skillet from the heat and stir in the lemon juice and vanilla extract. Transfer the apple filling to a bowl and cool completely before assembling the samosas.
1 tbsp (15 ml) fresh lemon juice, 1 tsp (5 ml) vanilla extract
Preheat the oven to 375°F (190°C). Line a large rimmed baking sheet with parchment paper.
Stir the granulated sugar and cinnamon together in a small bowl and set aside.
¼ cup (50 g) granulated sugar, 2 tsps (5 g) ground cinnamon
Place the stacked phyllo sheets on a clean work surface with the edges aligned. Cut through the entire stack lengthwise into three equal strips using a sharp knife or kitchen scissors. Keep the phyllo covered while working to prevent it from drying out and cracking.
12 sheets phyllo dough
Place one phyllo strip on the work surface and lightly brush with melted butter. Top with a second phyllo strip, aligning the edges. Place about 1 tablespoon of the cooled apple filling near the bottom of the strip, leaving enough phyllo around the filling to make the first fold.
6 tbsps (85 g) unsalted butter
Fold one bottom corner diagonally over the apple filling to form a triangle and enclose the filling. Continue folding the triangle up the length of the strip, keeping the edges aligned as you go. Lightly brush the final flap with melted butter to seal. Transfer to the prepared baking sheet and repeat with the remaining phyllo and apple filling to make 16 to 18 samosas.
Lightly brush the tops and edges of the samosas with the remaining melted butter. Sprinkle evenly with the cinnamon sugar.
Bake for 14 to 16 minutes, or until the phyllo is crisp and golden across the tops and folded areas. Begin checking at 14 minutes, as phyllo can brown quickly during the final few minutes of baking.
Serve the apple pie samosas warm with vanilla ice cream and warm caramel sauce, if desired.
vanilla ice cream, warm caramel sauce