3 ounces unsweetened chocolate, roughly chopped
1 stick unsalted butter, plus extra for pan
1 1/3 cups granulated sugar
2 large eggs
1 teaspoon vanilla extract
1/2 teaspoon flaky sea salt or 1/4 teaspoon table salt
2/3 cup all-purpose flour
Heat oven to 350°F. Line an 8×8-inch Line an 8×8-inch square baking pan with parchment, exentending it up two sides, or foil. Butter the parchment or foil or spray it with a nonstick cooking spray.
In a medium heatproof bowl over gently simmering water, melt chocolate and butter together until only a couple unmelted bits remain. Off the heat, stir until smooth and fully melted. You can also do this in the microwave in 30-second bursts, stirring between each. Whisk in sugar, then eggs, one at a time, then vanilla and salt. Stir in flour with a spoon or flexible spatula and scrape batter into prepared pan, spread until even. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out batter-free.
Let cool and cut into desired size. If desired, dust the brownies with powdered sugar before serving.