Oatmeal Fudge Bars

My mom asked me to make dessert yesterday to eat after we had Dad's famous ribs for dinner. After Dad's ribs, the dessert has to be amazing or it won't be remembered! These bars were pretty sensational, if I may say so myself. They are very rich, so an 8x8 pan could easily make 16 small servings. But we are a gluttonous family, so I cut mine into 12 pieces. The crispy, crunchy oat crust/topping is a wonderful accompaniment to the soft, fudgy center. This recipe is definitely a keeper!OATMEAL FUDGE BARS (from The America’s Test Kitchen Family Baking Book)
MAKES 16 bars
Old-fashioned rolled oats may be substituted for the quick-cooking oats, although the bars will be more chewy.
CRUST AND TOPPING
1 cup (3 ounces) quick-cooking oats
1 cup packed (7 ounces) light brown sugar
3/4 cup (3 3/4 ounces) all-purpose flour
1/4 teaspoon baking powder
1/4 teaspoon baking soda
1/4 teaspoon salt
8 tablespoons (1 stick) unsalted butter, melted and cooled

FILLING
1/4 cup (1 1/4 ounces) all-purpose flour
1/4 cup packed (1 3/4 ounces) light brown sugar
2 teaspoons instant espresso or instant coffee (if using granulated instant coffee, dissolve into 2 teaspoons hot water and stir into the chocolate mixture after the egg)
1/4 teaspoon salt
1 1/2 cups (9 ounces) semisweet chocolate chips
2 tablespoons unsalted butter
1 large egg

1. FOR THE CRUST AND TOPPING: Adjust an oven rack to the middle position and heat the oven to 325 degrees. Line an 8-inch square baking pan with a foil sling and grease the foil.
2. Whisk the oats, brown sugar, flour, baking powder, baking soda, and salt together in a large bowl. Stir in the melted butter until combined. Reserve 3/4 cup of the oat mixture for the topping.
3. Sprinkle the remaining oat mixture into the prepared pan and press into an even layer with the bottom of a measuring cup. Bake the crust until light golden brown, about 8 minutes. Let the crust cool completely on a wire rack, about 1 hour.
4. FOR THE FILLING: Whisk the flour, sugar, instant espresso, and salt together in a medium bowl. Melt the chocolate chips and butter together in the microwave, stirring often, 1 to 3 minutes. Transfer the chocolate mixture to a large bowl and let cool slightly. Whisk in the egg until combined. Stir in the flour mixture until just incorporated.
5. Adjust an oven rack to the middle position and heat the oven to 325 degrees. Spread the filling evenly over the cooled crust and smooth the top. Sprinkle with the reserved oat topping. Bake the bars until a toothpick inserted into the center comes out with a few moist crumbs attached and the filling begins to pull away from the sides of the pan, 25 to 30 minutes, rotating the pan halfway through baking.
6. Let the bars cool completely in the pan, set on a wire rack, about 2 hours. Remove the bars from the pan using the foil, cut into squares, and serve.