Step 1: Prepare the Cookie Dough

• Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone mat.
• In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
• In a large bowl, beat the butter and brown sugar together with an electric mixer (or by hand) until creamy and smooth.
• Add the egg and vanilla extract to the mixture and beat until combined.
• Gradually add the dry ingredients to the wet mixture and mix until just combined. The dough should be soft but not too sticky.

Step 2: Make the Brown Sugar Filling

• In a small bowl, mix together the brown sugar, butter, flour, cinnamon, and a pinch of salt until smooth and combined. The filling should be thick and spreadable.

Step 3: Roll Out the Dough

• On a floured surface, roll out the dough to about 1/8 inch thickness.
• Using a knife or a pizza cutter, cut the dough into rectangles (about 2×3 inches in size).

Step 4: Assemble the Cookies

• Place half of the dough rectangles on a baking sheet, leaving some space between them.
• Spoon about 1 tsp of the brown sugar filling onto the center of each rectangle.
• Place the remaining dough rectangles on top, gently pressing down the edges to seal. You can use a fork to crimp the edges if desired, just like you would for a traditional pop tart.

Step 5: Bake the Cookies

• Bake the cookies in the preheated oven for 10–12 minutes, or until the edges are lightly golden and the cookies have puffed up slightly.
• Allow the cookies to cool on the baking sheet for a few minutes, then transfer them to a wire rack to cool completely.

Step 6: Glaze the Cookies (Optional)

• If you’d like to add a glaze, whisk together the powdered sugar, milk, and vanilla extract in a small bowl until smooth.
• Drizzle the glaze over the cooled cookies using a spoon or piping bag for a decorative touch.