Prep: preheat your oven to 350°. Line a 9x9 baking pan with parchment paper or spray with a cooking spray.
Melt: In a large microwave-safe mixing bowl: place the butter and 1/2 cup chocolate chips. Heat in the microwave in 30-second intervals until the butter and chocolate chips are melted, stirring between intervals. I had to heat mine for 90 seconds.
Mix: add in the sugar and whisk vigorously for 60 seconds, you want to incorporate as much sugar into the butter as possible, there will still be some visible sugar. Let cool for 5-10 minutes.
Add Ingredients: add in the eggs, egg yolk and vanilla and whisk vigorously for 60 seconds. This is what will give the brownies a shiny top.
Sift Dry Ingredients: in a fine mesh colander, add the flour, cocoa, ground flax seeds, brewers yeast and salt, and gently sift into the wet ingredients.
Add Dry Ingredients: gently fold together the wet and dry ingredients. You do not want to overmix.
Add Chocolate Chips: add in 3/4 cup of the chocolate chips into the brownie batter and gently fold them together. You do not want to overmix.
Pour: pour the brownie batter into your baking dish and sprinkle with the remaining chocolate chips.
Bake: place the baking pan in the oven and bake for 25-30 minutes, or until a toothpick comes out with moist crumbs. Sprinkle with flaky salt (if using). Let cool for 2-3 hours, then take out the brownies by carefully lifting out the parchement paper and placing them on a cutting board. Cut into the size you prefer.
Eat: serve and enjoy!