Preheat oven to 325°F. Grease a half-sheet pan with butter or nonstick spray. Place a piece of parchment paper on the greased pan. Set aside. (See Tip 4)
Whisk together the dry ingredients - flour, unsweetened cocoa powder, baking soda, and salt in a medium bowl. Set aside.
Combine the vegetable oil and bittersweet chocolate chips 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. Add sugar and vanilla extract. Beat on high until satiny, about 30 seconds. (See Tip 5)
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 mini chocolate chips and the toasted pecan pieces. The batter will be thick.
Transfer the brownie brittle batter to the prepared baking pan and spread in a thin layer. (See Tip 6)
Bake in a preheated 325°F oven for 30 to 35 minutes or until crispy. (See Tip 7)
Remove from the oven. Allow to cool completely and break into pieces.
YieldL: 12 servings (See Tip 8)