Preheat oven to 350 degrees then line a 9x13” baking pan with foil or parchment paper and spray with nonstick spray. Set aside.

Add baking chocolate and butter to a large, microwave safe bowl then microwave for 1 minute and 30 seconds. Whisk until chocolate is smooth, microwaving for 15-30 more seconds if needed to fully melt chocolate. Add sugar then whisk to combine. Add eggs and vanilla then whisk to combine. Add flour then stir to combine.

Pour batter into prepared baking dish then bake for 30-35 minutes or until a toothpick inserted into the center of the brownies comes out with fudgy crumbs. Err on the side of underbaking vs overbaking. Check brownies at the 10 minute mark - if sides are browning too quickly, gently place a piece of foil on top then continue baking. Cool completely then remove brownies from pan, slice and sprinkle with powdered sugar, if desired, before serving.