Step 1

Preheat the oven to 325°F. Line a 9x9-inch pan with parchment paper and spray lightly with cooking spray.

Step 2

In a medium mixing bowl, combine the flour, oats, both sugars, baking powder, baking soda, and salt. Stir with a whisk to combine.

Step 3

Stir in the melted butter until combined.

Step 4

Set aside 1 cup of the mixture to use for the topping. Press the remaining mixture into the bottom of the prepared pan.

Step 5

Bake for 8 minutes until light golden brown. Set aside to cool while you make the filling.

Step 6

In a small mixing bowl, combine the flour, sugar, and salt. Stir with a whisk to combine.

Step 7

Place chocolate and butter in a large heat-proof bowl set over a pot of barely simmering water. Stir with a silicone spatula until chocolate has melted completely. Remove from heat.

Step 8

Whisk in the eggs, one at a time. Stir in the flour mixture until combined. The mixture will resemble thick brownie batter.

Step 9

Pour over the cooled crust. Sprinkle the top with the remaining oatmeal mixture.

Step 10

Bake for 30 to 35 minutes, until the edges are set and have browned lightly. Cool in the pan on a wire rack for 1 hour.

Step 11

Remove from pan and cut into squares. For neat slices, refrigerate for 2 hours before cutting.