Preheat oven to 350F (177C). Line a square (9x9) baking dish with parchment paper.
In a large bowl cream the butter and sugar until soft and fluffy. I like using my stand mixer with a paddle attachment for this.
Add 1/3 cup coffee powder and mix to combine.
Add 4 eggs, and mix to combine once more.
Add 1 1/2 cups flour, 1 cup cocoa powder, 1/2 tsp salt, 1/2 tsp vanilla and mix to combine. If you are using a stand mixer, go slow. I recommend starting to mix with a spatula by hand so the flour doesn't go flying when you turn on the mixer. Don't over mix.
The dough with be quite thick. Pour the brownie batter into the lined baking tin. Spread evenly and sprinkle with chocolate chips, if using, and flakey sea salt.
Bake for 30-35 minutes until set in the centre. Allow to cool for 10 minutes before removing from pan to cut and serve. Enjoy!