Preheat oven to 350 degrees. Butter and flour a 12x18x1-inch baking sheet. Add candy bars to a plastic zipper bag. Smash into small-medium pieces. Keep in the fridge until ready to use to avoid melting.
Melt butter, chocolate chips, and unsweetened chocolate in a large glass bowl over simmering water. Once fully melted, set aside to cool slightly (you don't want to cook the eggs when combined). In a separate large bowl, combine eggs, coffee granules, vanilla, and sugar together with a wooden spoon (not beaters). Stir in the cooled chocolate mixture into the egg mixture. Let sit to room temperature.
In a medium bowl combine flour, baking powder, and salt. Stir into the chocolate mixture. Pour into the prepared baking sheet. Sprinkle a small amount of the crushed candy bars over the top, leaving most of the candy bars for AFTER baking.
Bake for 20 minutes, then bang the pan a couple times against the oven shelf (Ina says so) to get the air to escape from the pan. Bake for another 12-15 minutes or until toothpick comes out clean. Allow the brownies to rest for about 10 minutes. Sprinkle the rest of the candy bars over the top. Cool, cut, and serve!