If you like Girl Scout Thin Mint cookies, you'll love these deeply chocolate, strongly mint brownies. The slash of white filling through the center is striking; and the rich, thick chocolate ganache topping is spectacularly delicious!

Mint Filling
4 cups (16 ounces) confectioners' sugar
6 tablespoons (3 ounces) unsalted butter
6 tablespoons (2 5/8 ounces) vegetable shortening*
1/4 teaspoon peppermint oil, or 1 to 2 teaspoons peppermint extract (to taste)
1/4 cup (1 ounce) King Arthur Unbleached All-Purpose Flour or Signature Secrets Culinary Thickener (3/4 ounce)
6 tablespoons (3 ounces) heavy cream

Brownie Batter
1 cup (2 sticks, 8 ounces) unsalted butter
1 pound (about 2 generous cups) brown sugar
1 cup (4 ounces) Dutch-process cocoa
1 teaspoon salt
1 teaspoon baking powder
1 tablespoon vanilla extract
4 large eggs
1 1/2 cups (6 1/4 ounces) King Arthur Unbleached All-Purpose Flour
2 cups (12 ounces) chocolate chips

*Usually we don't use vegetable shortening due to its trans-fat content; but in this case it's necessary, to keep the filling from melting into the batter as the brownies bake.

To make the mint filling: Beat the filling ingredients together till they're cohesive; the mixture will be the consistency of stiff cookie dough. Spread the filling, on a piece of lightly greased plastic wrap, into a rectangle just slightly smaller than a 9" x 13" pan; this is most easily done on the outside bottom of a 9" x 13" pan that you've covered with plastic wrap. Cover the filling with wrap, and refrigerate overnight, or till thoroughly chilled.

Preheat the oven to 350°F. Lightly greased a 9" x 13" pan.

To make the brownie batter: In a medium-sized microwave-safe bowl, or in a saucepan set over low heat, melt the butter, then add the sugar and stir to combine. Return the mixture to the heat (or microwave) briefly, till it's very hot, but not bubbling; it'll become smooth and shiny looking. The sugar and butter will separate; that's OK, just stir till some of the butter has been reabsorbed. Heating this mixture a second time will dissolve more of the sugar, which will yield a shiny top crust on your brownies; very attractive, should you choose not to cover the brownies with ganache.

Stir in the cocoa, salt, baking powder, and vanilla. Whisk in the eggs, stirring till smooth; then add the flour and chips, again stirring till smooth. Spoon half the batter (about 28 ounces) into the prepared pan. Using the plastic wrap as a sling to move the filling, slide it atop the batter. Top with the remaining batter.

Bake the brownies for about 40 minutes, until a cake tester inserted into the center comes out clean, or with just a tiny amount of crumb clinging to it. Remove the brownies from the oven, and cool them completely before icing with ganache. Allow the icing to set before cutting and serving the brownies. Yield: 2 dozen brownies.

Chocolate Ganache Icing

Heavy cream. Chocolate. That's it. You can't go wrong.

2 cups (12 ounces) chocolate chips or chopped semisweet or bittersweet chocolate
1 cup (8 ounces) heavy cream or whipping cream

In a microwave-safe bowl, or in a small saucepan set over medium heat, heat the cream till it's very hot. You should see wisps of steam beginning to rise from it, and some very tiny bubbles around the edge. Add the chocolate to the cream, and stir till smooth. Don't panic—at first, the mixture will look disarmingly soupy, but just keep stirring. Very shortly it'll become a rich brown, thick, shiny spreadable icing. Yield: 2 cups icing.