Preheat oven according to cookie package directions. On a floured surface, use hands to slightly flatten cookie dough to an 8x2 1/2 inch log. Place on baking sheet, then freeze for 30 minutes. Slice dough in half lengthwise, then slice each half in 16 slices. Place slices on ccokie sheet. Using a fork dipped in sugar, make crisscross pattern on each cookie. Bake cookies according to package directions or until golden brown. Cool on wire racks.
Preheat oven to 350 degrees. Line the bottom and sides of a 8x8x2 inch baking pan with heavy foil, extending foil over pan edges. Grease foil; set pan aside. In a medium pan, stir butter and chocolate over low heat just until melted. Remove from heat. Using a wooden spoon, stir in sugar and vanilla. Cool 5 minutes. Add eggs, one at a time to butter-chocolate mixture, beating after each just until combined. Stir in flour and cocoa powder. Evenly spread batter in prepared pan. Bake 30-35 minutes, just until a wooden toothpick inserted near the center comes out clean. Transfer to wire rack. Leave oven set to 350 to warm sandwich cookies.
Scoop and mash warm brownies onto the flat side of a cookie. Top with 1 tsp preserves and a second cookie. Place sandwich cookies that will be served immediately on a cookie sheet and warm in oven about 3-4 minutes.