Preparation

• Position a rack in the middle of the oven and heat to 325° F. Lightly grease the bottom and sides of a 9×13-inch baking pan.
• In a medium bowl, whisk the flour, baking powder, and salt to blend. Melt the butter in a large saucepan over medium heat, stirring occasionally. Remove the pan from the heat and whisk in the cocoa powder until smooth. Whisk in the brown sugar until blended. Add the eggs, one at a time, whisking until just blended. Whisk in the coffee liquer along with the last egg. Sprinkle the flour over the mixture and stir with a rubber spatulla until just blended. Scrape the batter into the prepared pan and spread it evenly. Bake until a toothpick inserted in the center comes out with a few small, moist clumps sticking to it, about 30 minutes. (Don’t overbake, or the squares won’t be fudgy.) Transfer the pan to a rack to let cool completely.

Make the chocolate glaze:

• In a medium bowl, melt the chocolate, butter and corn syrup in a microwave or over barely simmering water, whisking until smooth. Pour the glaze onto the center of the cooled, uncut fudge bars. Using an offset spatula, spread the glaze evenly to cover completely. Refrigerate until the glaze is set, about 30 minutes. Cut into 1-inch squares.