We could never turn down a brownie sandwiched between two cookies.
This recipe is courtesy of All Recipes.
Preheat oven to 325 degrees F.
Melt butter and chocolate over low hot in a medium saucepan, stirring constantly. Remove from the heat and let cool slightly.
Stir the sugar into the cooled chocolate. Add the eggs, one at a time, beating with a spoon until just combined. Stir in the vanilla.
Stir together the flour and baking soda. Add the flour mixture to the chocolate mixture. Stir until just combined. Press half the cookie dough into an 8-by-8-inch pan. Spread brownie batter over the cookie dough. Crumble remaining cookie dough evenly over brownie batter. Press down slightly.
Bake for 50-55 minutes, until edges are firm and starting to pull away from the sides of the pan. Cool on a wire rack before cutting into bars.