Preheat oven to 350°F. Grease and flour a 13 x 9 x 1 1/2-inch sheet pan.
Melt together the butter, 8 ounces of chocolate chips, and unsweetened chocolate on top of a double boiler. Cool slightly.
Stir together the eggs, instant coffee, vanilla and sugar. Stir in the warm chocolate mixture and cool to room temperature.
Stir together 1/2 cup of the flour, baking powder, and salt. Add to cooled chocolate mixture.
Toss the 6 ounces of chocolate chips with 1 tablespoons flour to coat. Strain the chocolate chips through a fine mesh sieve/strainer to remove excess flour, then add the chocolate chips to the batter. Pour into prepared pan.
Bake for about 30 minutes, or until tester just comes out clean. Halfway through the baking, rap the pan against the oven shelf to allow air to escape from between the pan and the brownie dough. Do not over-bake!
Cool thoroughly, refrigerate well, and cut into squares.
Notes
Some people prefer these cold, some at room temperature, and some heated up with vanilla ice cream.Source: Adapted from Food Network, originally from Ina Garten's The Barefoot Contessa CookbookYou're Gonna Bake It After Allbakeitafterall.com