01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing excess paper to hang over the sides for easy removal.
02 - In a medium mixing bowl, blend flour, brown sugar, cinnamon, and salt. Cut in cold butter with a pastry cutter or fork until combined and crumbly. Refrigerate until needed.
03 - In a small bowl, whisk together flour, baking powder, and salt until evenly incorporated.
04 - In a large bowl, cream softened butter and granulated sugar using an electric mixer until light in texture. Beat in egg, vanilla extract, and brewed coffee until homogeneous.
05 - Add dry ingredients to creamed mixture in increments, mixing just until incorporated. Evenly spread batter in prepared pan using a spatula.
06 - Distribute chilled streusel mixture uniformly over batter.
07 - Bake in the center of oven for 30 to 35 minutes, until top is golden and a toothpick inserted into the center exits clean.
08 - Allow bars to cool completely on a cooling rack in the pan. For the glaze, whisk powdered sugar and brewed coffee together until smooth. Drizzle over cooled bars.
09 - Lift bars from pan using parchment paper, then slice into 12 even squares before serving.