Begin by creaming 1 cup of unsalted butter with 1/2 cup brown sugar and 1/2 cup granulated sugar in a large bowl until the mixture is light and fluffy, about 3–5 minutes. Next, add in 2 eggs and 2 teaspoons of vanilla extract, mixing well until fully combined, creating a rich and creamy dough base.

In a separate bowl, whisk together 3 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/4 teaspoon of salt. Gradually add this dry mixture to the butter mixture, stirring gently until just combined. Be careful not to overmix, as this will keep your Brown Sugar Pop Tart Cookies tender and delightful.

In a small bowl, mix together 1/2 cup of brown sugar, 1 teaspoon of cinnamon, and 2 tablespoons of milk until you achieve a smooth consistency. This sweet filling will provide a gooey center.

Divide the dough into two equal portions. On a lightly floured surface, roll out each portion to about 1/4 inch thick. Aim for a rectangular shape, as this will make it easier to cut into squares for your cookies.

Using a sharp knife or a cookie cutter, cut the rolled dough into squares or rectangles, around 3x4 inches. Place a teaspoon of the prepared filling in the center of half of the cut dough pieces. Top each with the remaining dough pieces, pressing the edges to seal them tight.

Preheat your oven to 350°F (175°C). Arrange the assembled cookies on a baking sheet, leaving space between each one. Bake in the preheated oven for approximately 12–15 minutes, or until the edges turn lightly golden brown.

Once baked, allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack. While they cool, prepare the icing by mixing 1 cup of powdered sugar with 2 tablespoons of milk until smooth. Drizzle the icing over the cooled cookies, adding sprinkles for a festive touch if desired.