Prep the baking sheets. Preheat your oven to 325°F. Position oven racks in the upper-middle and lower-middle sections. Then, line two rimmed baking sheets with parchment paper.
Make the dough. Using an electric mixer on medium speed, cream the room-temperature butter and packed brown sugar until the mixture is light and fluffy (about 2–3 minutes). Then, slowly add 2 cups of flour, mixing at low speed until combined. The dough will look crumbly—avoid adding any liquid at this stage. Next, transfer the dough onto a floured surface. Knead in the remaining ¼ cup of flour by hand until the dough holds together.
Roll out and cut. Roll the dough to a ½-inch thickness on the floured surface. If the dough sticks, lightly dust the rolling pin with flour. Then, cut the dough into roughly 3 inches-long and 1-inch-wide rectangles. Place the cut pieces onto the prepared baking sheets, leaving at least 1 inch of space between each cookie.
Bake and cool. Bake for 20 minutes until the cookies are set, and the edges are lightly golden. Allow the cookies to cool completely on a wire rack before moving to the chocolate-dipping step.
Dip and decorate. In a microwave-safe bowl, combine the chocolate chips and shortening. Then, stirring halfway through, melt in the microwave on LOW power for about 45 seconds. If needed, microwave in 10-second intervals until fully melted and smooth. Dip one end of each cooled cookie into the melted chocolate. Place the dipped cookies on wax or parchment paper to set. While the chocolate is still melted, add sprinkles to the dipped ends if desired. If the chocolate hardens before you finish, reheat it briefly in the microwave.