Preheat oven to 350 degrees and line an 8 inch square baking dish with parchment paper. Lightly grease the inside of the parchment paper.
Create a double boiler setup with a soup pot filled with a few cups of water and then place the stainless steel mixing bowl on top. Turn the heat to medium. Add the vegan butter and chocolate. USing a wooden spoon, stir continuously until fully melted. About halfway through, turn the stove heat to low so you don't burn the chocolate. turn off heat and remove bowl from heat.
Add in the sugars, vanilla extract, salt, cacao powder and egg replacer of choice. See notes. Briskly stir or whisk until smooth.
Stir in the flour and starch until silky smooth. your batter should be nice and glossy. Fold in optional nuts and additional chocolate chips.
Pour the chocolate mixture into the brownie pan.
Bake at 350 for 30-35 minutes
Pull from oven and sprinkle optional coarse sea salt on top. I love fleur de sel if you have it!
Allow brownies to cool for at least twenty minutes before slicing and serving. Best served warm. Store leftovers in the fridge.