Preheat oven to 325°F. Grease a 13-inch x18-inch sheet pan and place a piece of parchment paper on the greased pan. This will ensure the parchment paper does not slide around when you are spreading the thick brownie brittle batter. Set aside.

Whisk together the dry ingredients in a medium bowl and then set aside.

Combine the vegetable oil and bittersweet chocolate in a microwave-safe dish. Microwave on 50% power in 30-second increments until the chocolate is melted, about 1 minute and 30 seconds. Stir to combine. Allow to cool slightly.

Beat egg whites on high in a medium bowl until frothy, about 20 seconds (this can be done with a wire whisk instead of a mixer). Add sugar and vanilla extract. Beat on high until satiny, about 30 seconds.

Add the chocolate mixture to the egg whites. Beat on high until well combined, about 20 seconds.

Add the dry ingredients to the egg-white mixture. Beat on low just until combined. Fold in the semi-sweet chocolate chips and the toasted pecan pieces, saving some to sprinkle over the top. The batter will be thick.

Transfer the brownie brittle batter to the prepared baking sheet and spread it into a thin layer. It doesn’t need to reach the edges, but you’ll want to spread it as thinly as possibly, keeping the layer a somewhat even thickness. Sprinkle remaining pecan pieces on top.

Bake for 30-35 minutes or until crispy. Remove from the oven and allow to cool completely. Break into pieces. Enjoy!