Preheat The Oven & Prep Your Pan. Star by preheating The Oven To 350 degrees F. Line an 8x8 square metal baking pan with parchment paper. (Use a METAL pan, not a glass pan or the brownies won't rise the same.)
Combine The Dry Ingredients. In a medium bowl, combing gluten-free flour, cocoa powder, and salt. Whisk to combine and to break up any clumps of cocoa. Set flour mixture aside.
Melt Butter, Milk & Sugar. In a small saucepan, combine vegan butter, milk, and sugar. Stir over medium low heat, whisking until the sugar is completely dissolved. (No gritty or grainy texture left!) Do not let the mixture simmer or boil, just heat it long enough to melt the butter and dissolve the sugar completely.
Stir In The Chocolate & Vanilla. Remove the pan from the heat and stir in 1 cup of chocolate chips and the vanilla extract. Whisk until the chocolate is fully melted. Let the mixture cool 3-5 minutes, so it doesn't melt the remaining chocolate chips later.
Add In The Dry Ingredients. Stir in the dry ingredients until just combined. The brownie batter will be thick, shiny, and sticky. If it's still quite warm, let it cool another few minutes before adding the chocolate chips.
Fold In The Chocolate Chips. Add the remaining 2/3 cup chocolate chips and gently fold in with a spatula to combine. Pour the brownie batter into your prepared pan and smooth the surface.
Bake The Brownies. Pop the brownies in the oven and bake for 25-27 minutes, or until the edges are set and the center isn't jiggly. A toothpick inserted in the center will likely come out with a bit of thick batter, but it shouldn't be thin or liquid. (Keep in mind that the brownies will continue to set as they cool. Try not to over-bake the brownies or you'll lose the fudgy texture. If your toothpick comes out clean or with just a few moist crumbs, the brownies are likely over-baked.)
Cool & Cut. Let the brownies cool completely before cutting. (I know it's hard to wait, but if you cut them warm, they'll likely be too gooey. Let them set, as they'll continue to cook as they cool. Cut into 9 large squares, 12 rectangles, or 16 small squares. (Or even smaller pieces, if desired!)
Serve & Store. Enjoy at room temperature or store in an airtight container. Vegan brownies will keep at room temperature 2 days, in the refrigerator 3-4 days, or you can freeze them up to 1 month.