Brownies

Heat the oven to 350F (175C)

Butter a 9 by 13 inch baking pan, then line it with parchment paper that hangs over two sides. The overhang lets you lift the whole slab out for clean cutting.

Melt the butter with the sugar

Melt the butter in a large saucepan over low heat. Take it off the heat and stir in the sugar, cocoa, and salt until the mixture looks like wet sand with no dry cocoa left. Let it cool for 5 minutes so the eggs do not scramble when they go in.

Beat in the eggs and vanilla

Add the eggs one at a time, stirring hard with a wooden spoon or whisk after each. Stir in the vanilla. The batter turns from grainy to thick and glossy as the eggs go in, and that shine is what gives the baked top its crackly finish.

Fold in the flour

Stir the flour and baking powder together, then add them to the pan and fold just until no white streaks remain. Fold in the chocolate chips if using. Do not beat the batter once the flour is in, or the brownies turn cakey.

Spread the batter into the pan

Scrape the batter into the prepared pan and push it into the corners with a spatula. It is thick and will not level itself, so smooth the top.

Bake until a toothpick comes out with moist crumbs

Bake for 25 to 32 minutes. The brownies are done when the top is set and shiny, the edges have pulled slightly from the pan, and a toothpick inserted 2 inches from the edge comes out with a few moist crumbs, not wet batter. A clean toothpick means they are overbaked.

Cool before cutting

Let the pan cool completely on a wire rack, at least 1 hour. Lift the slab out by the parchment and cut into 24 squares with a sharp knife, wiping the blade between cuts.

Storage. Keep brownies in an airtight container at room temperature for up to 4 days, or wrap individual squares and freeze for up to 3 months.