Begin by peeling and chopping your Honeycrisp apple into small cubes. In a medium saucepan over medium heat, combine the apple pieces with brown sugar, vegan butter, lemon juice, and pumpkin pie spice. Stir occasionally for about 5-7 minutes until the mixture is bubbling and the apples are tender. Mix cornstarch with a splash of water to create a slurry, then add it to the sauce and cook until thickened, around 2-3 minutes. Let your filling cool while you make the cookie dough.

In a large mixing bowl, cream together 1/4 cup vegan butter and 1/2 cup brown sugar until smooth and fluffy—this should take about 3-5 minutes. Add in your prepared flax egg and a teaspoon of vanilla extract, mixing until well blended. Gradually incorporate your dry ingredients: all-purpose flour, cornstarch, and pumpkin pie spice. Combine until a thick dough forms. Once mixed, cover and chill the dough in the refrigerator for 30 minutes to 1 hour.

Preheat your oven to 350°F (175°C) while the dough chills. Line a baking sheet with parchment paper. Scoop out portions of the chilled dough and roll them into balls, about 1.5 tablespoons each. Roll the dough balls in a little brown sugar before placing them on the prepared sheet. Once all the cookie dough is on the sheet, create an indent in each ball using your thumb, making sure to leave some room for the apple filling.

Using a spoon, fill each indent in the cookie dough balls with the cooled apple pie filling. Carefully bake the cookies in the preheated oven for 14-16 minutes, or until the edges are crisp and the centers appear slightly gooey and golden. Once done, remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.