Preheat your oven to 350 degrees.

In a stainless steel or light colored pan, heat to medium and start to brown 1 cup of butter. Stirring frequently and keeping your eye on it so it doesn't burn. This process should take about 12-15 minutes. You will start to see golden brown bits at the bottom of the pan when it is ready. Scrape it all into a bowl and set aside.

Add in your dark chocolate chips to your browned butter and whisk together until completely melted. Set aside.

In a medium sized bowl, whisk together your dry ingredients - flour, dutch cocoa, salt, and espresso powder. Set aside.

In another bowl, mix your eggs, vanilla, white sugar, brown sugar, and coffee concentrate with a hand or standing mixer. Mix until fluffy (about 2-3 minutes).

Putting your mixer to low setting, slowly drizzle in your melted chocolate and mix until combined.

Add in your dry ingredients and fold in with a spatula.

Line an 8x8 metal baking pan with parchment paper and pour your batter into the pan. Bake for 30-35 minutes. Every oven is different! I baked mine for 32 minutes and it was perfect. To test the doneness, insert a toothpick and if it comes out clean, remove your brownies from the oven. Please keep in mind if you are using anything besides a metal pan (glass or ceramic) your brownies will bake SLOWER and will require more time in the oven - closer to 45 minutes.

Remove from oven and set on a cooling rack (while still in the pan) and cool for 45 minutes to 1 hour (do not skip this step as it helps your brownies hold their shape).

Sprinkle with flakey sea salt and cut into 3x3 squares and enjoy!