In a large bowl, whisk together flour, sugar, pumpkin spice, and salt until evenly combined.

Add chilled, cubed vegan butter and use a pastry cutter or fingers to blend until mixture resembles coarse crumbs.

Drizzle ice water over the dry mix a tablespoon at a time, tossing with a fork until dough clings together in a soft ball.

Transfer dough to a floured surface and flatten into a disk, wrap and chill for at least 20 minutes.

Meanwhile, combine pumpkin puree, maple syrup, cornstarch, plant-based milk, and vanilla in a small bowl, stirring until smooth and thickened.

Preheat oven to 180°C (350°F) and line a baking sheet with parchment paper.

Roll chilled dough to about 1/8-inch thickness on a floured surface.

Cut dough into rectangles (about 3×4 inches) and place half on the prepared sheet.

Spoon a tablespoon of pumpkin filling onto the center of each bottom rectangle, leaving a border clear.

Lightly brush edges with plant-based milk and top with remaining dough rectangles.

Press edges together firmly with a fork to seal, then poke a few holes on top to vent steam.

Bake until golden and puffed, about 15–20 minutes, watching closely for even color.

Cool slightly while whisking powdered sugar, extra milk, and vanilla to a smooth glaze.

Drizzle glaze over warm pop-tarts and sprinkle sugar on top; allow the glaze to set before serving.