Preheat oven to 350°F.
Line 9 x 13 inch pan with foil or parchment paper with overhangs for easy removal.
In large bowl, put cocoa powder, chopped chocolate and espresso powder.
Brown Butter: Do not leave stove unattended as browning butter happens fast.
Add butter to light-colored saucepan over medium-low heat. Keep stirring throughout entire process.
Once the butter is melted, it will begin to foam and sizzle around the edges. Keep stirring and scraping bottom with a spatula.
Grainy white milk solids and foam will appear. Keep stirring.
As you stir, in about 5–8 minutes (or less depending on stovetop) from start, the butter will turn golden brown. It will start to smell buttery and nutty.
Quickly remove the pan from heat and pour the browned butter into large bowl containing cocoa powder, espresso powder and chopped chocolate. Stir until smooth. Set aside to cool.
In separate large bowl, using stand or hand mixer, whip white sugar, brown sugar, vanilla and eggs on medium-high (level 5 out of 10) until thick, fluffy, and lightened in color (approximately 4-5 minutes). Don't skip whipping as it is key to glossy crackly brownie tops!
Reduce speed to low. Slowly pour chocolate and butter mixture into egg and sugar mixture until fully incorporated.
Gently fold in flour and kosher salt (with spatula).
Mix in ½ cup cocktail cherries.
Scoop and spread batter evenly into prepared pan.
Top with ¼ cup remaining cocktail cherries.
Bake 25 minutes until surface is glossy and center is set (no jiggle).
Let cool at least 30 minutes before removing from pan to slice.