Make the dough - In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy. Add the egg and mix until combined. Gradually add the flour, mixing until a dough forms. Divide the dough in half and shape each half into a disk. Wrap disks in plastic wrap and refrigerate for 30 minutes. - Make sure the butter is at room temperature. If it's too cold, it won't incorporate properly into the dough and will result in a tough cookie. If it's too warm, the dough will be sticky and difficult to work with.

Make the caramel filling - In a small saucepan, bring the dark corn syrup and heavy cream to a boil. Reduce heat and let simmer for 5 minutes, stirring occasionally. Remove from heat and let cool to room temperature. - Be careful when working with hot syrup, as it can cause burns if it comes into contact with your skin.

Preheat the oven - Preheat the oven to 350°F. Line a baking sheet with parchment paper. - Make sure the oven is fully preheated before sliding in the cookies to ensure even baking.

Roll out the dough - On a lightly floured surface, roll out one of the dough disks into 1/4 inch thickness. Cut out 24 rounds using a 3 inch cookie cutter. Repeat with the other dough disk. - If the dough feels too firm, let it sit at room temperature until pliable.

Assemble the cookies - Place half of the dough rounds on the prepared baking sheet. Spoon 1 to 2 teaspoons of caramel filling onto each round, leaving a 1/4 inch border around the edges. Top with the remaining dough rounds and press down to seal the edges together. - Make sure to leave a small space around the edges of the dough to prevent the filling from leaking out.

Bake the cookies - Bake for 15-20 minutes, or until the cookies are lightly golden brown. Let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. - Be careful not to overbake the cookies, or they will become too crispy and lose their chewy texture.