Preheat oven to 325°F.

Line a half-sheet pan (18-inches by 13-inches by 1/2-inch) with parchment paper and set aside.

In a mixing bowl, vigorously whisk the egg whites until frothy, about 1 minute. Whisk in the sugar until completely incorporated. Add the oil, water, and vanilla extract and whisk until completely combined. Dump in the flour, cocoa powder, baking soda, and salt and whisk until you have a totally smooth and shiny brownie batter. Scrape onto the lined pan and use an offset spatula (or silicone spatula) to spread the batter as thinly and evenly as possible. It should come very close to the edges of the parchment leaving perhaps a 1/2-inch border all around if you have it as thin as you should. Sprinkle the toffee bits and chocolate chips evenly over the surface of the batter. You do not need to press them in for them to stick.

Bake for 15 minutes, remove the pan, score into desired sizes, then return the pan to the oven for an additional 10 minutes. Let cool completely before breaking along the scored lines. Store in an airtight container at room temperature for up to a week. If they start getting soft, you can re-crisp them in a 250°F oven.