Brownie Brittle With Chocolate Chips & Toffee Bits

Preheat the oven to 350 degrees. Line two 9X13 rimmed quarter sheet pans with parchment. Spray lightly with canola cooking spray.
In a large microwave safe mixing bowl, add the butter and 1 cup of chocolate chips. Microwave for 30 seconds and stir with a large rubber spatula. Return to the microwave for 15 seconds at a time, stirring after each, until the mixtures is completely melted and smooth.
With a large rubber spatula, stir in the cocoa and sugar; the mixture will be thick and grainy. Stir in the egg whites, milk and vanilla extract; stir just until smooth.
In a medium mixing bowl, whisk together the flour, baking soda, espresso powder and salt. Gradually stir into the butter/chocolate mixture until smooth and thick.
Divide the batter between the 2 sheet pans. Take your time and smooth the batter into the corners and evenly spread around the pan. Sprinkle the mini chocolate chips (2 tablespoons on each) and toffee bits (1 tablespoon on each). Bake for 15 minutes or until glossy but still moist. Do not let the edges burn. The brownies will be slightly soft while hot. Remove from the oven and immediately use a pizza cutter to cut 12 squares in each pan. Let the brownies cool completely in the pan. They will harden as they cool.
Remove from the pan onto a flat surface. Gently break the pieces along the lines. Trim off any burnt or well done edges. Set the pieces on a tray lined with waxed paper to crisp and harden further.