Makes 36 bars
| Crust and Topping | |
| 3/4 | cup all-purpose flour |
| 1 | cup quick-cooking oats |
| 1 | cup packed light brown sugar |
| 1/4 | teaspoon baking powder |
| 1/4 | teaspoon baking soda |
| 1/8 | teaspoon salt |
| 8 | tablespoons (1 stick) unsalted butter , melted and cooled slightly |
Filling | |
| 1/2 | cup all-purpose flour |
| 1/2 | cup packed light brown sugar |
| 1 | tablespoon instant coffee granules or espresso powder |
| 1/4 | teaspoon salt |
| 2 | cups semisweet chocolate chips |
| 4 | tablespoons unsalted butter , chopped |
| 3 | large eggs |
1. For the crust: Adjust oven rack to middle position and heat oven to 325 degrees. Prepare 9 by 9-inch baking pan (see note below). Whisk flour, oatmeal, sugar, baking powder, baking soda, and salt in bowl. Stir in butter until combined. Set 11/4 cups oatmeal mixture aside. Press remaining oatmeal mixture firmly into prepared pan. Bake until light golden brown, about 8 minutes. Cool completely.
2. For the filling: Whisk flour, sugar, instant coffee, and salt in bowl. Melt chocolate and butter in large bowl; whisk in eggs, then stir in flour mixture. Pour filling over cooled crust and sprinkle with reserved oatmeal mixture.
3. Bake until toothpick inserted into center comes out with few crumbs attached, 35 to 40 minutes. Cool to room temperature, at least 1 hour. Cut into 1 1/2-inch squares.
Note: For all bar cookies, line baking pan with aluminum foil, allowing excess to overhang pan edges. Spray foil with cooking spray. When bar cookies are cooled, use foil overhang to lift bars from pan. All bar cookies can be refrigerated for up to 3 days.
