Preheat your oven to 350°F. Line an 8x8-inch metal baking pan with parchment paper, leaving a 2-inch overhang at all sides.

Place chocolate and butter in a heatproof bowl set over a saucepan of barely simmering water and stir until the chocolate is completely melted and smooth. You can also melt it in the microwave with frequent stirring after 20 second bursts. The chocolate should feel very warm. Remove it from the heat and do not let it cool – move on to the next step immediately.

Add eggs and sugar and whisk vigorously or mix with a wooden spoon until smooth and glossy. The batter will tighten up and look glossy when it is properly combined. Mix in vanilla and salt. Sprinkle the flour over the batter and fold it in gently.

Spread batter evenly into prepared pan and smooth out the top. Bake for 22-26 minutes until a toothpick inserted into the center comes out with a few moist crumbs attached and the top is shiny crinkly and puffed. It will sink as it cools. Transfer pan to a wire rack and let cool completely in the pan before slicing. For even fudgier brownies, let them set overnight in the fridge before slicing.