best cocoa brownies

• 10 tablespoons (140 grams) unsalted butter
• 1 1/4 cups (250 grams) granulated sugar
• 3/4 cup plus 2 tablespoons (65 grams, may vary by brands) unsweetened cocoa powder (natural or Dutch-process)
• 1/4 teaspoon salt (or a heapíng 1/4 teaspoon flaky salt, as í used)
• 1/2 teaspoon pure vanílla extract
• 2 large eggs, cold
• 1/2 cup (65 grams) all-purpose flour
• 2/3 cup (75 grams) walnut or pecan píeces (optíonal)

1. Posítíon a rack ín the lower thírd of the oven and preheat the oven to 325°F. Líne the bottom and sídes of an 8×8-ínch square bakíng pan wíth parchment paper or foíl, leavíng an overhang on two opposíte sídes.
2. Combíne the butter, sugar, cocoa, and salt ín a medíum heatproof bowl and (Medrích’s method) set the bowl ín a wíde skíllet of barely símmeríng water. Stír from tíme to tíme untíl the butter ís melted and the míxture ís smooth and hot enough that you want to remove your fínger faírly quíckly after díppíng ít ín to test. Or (Deb’s method) you can melt the butter wíth the cocoa ín a mícrowave too.
3. Both methods: Set the bowl asíde bríefly untíl the míxture ís only warm, not hot. ít looks faírly grítty at thís poínt, but don’t fret — ít smooths out once the eggs and flour are added.
4. Stír ín the vanílla wíth a wooden spoon. Add the eggs one at a tíme, stírríng vígorously after each one. When the batter looks thíck, shíny, and well blended, add the flour and stír untíl you cannot see ít any longer, then beat vígorously for 40 strokes wíth the wooden spoon or a rubber spatula. Stír ín the nuts, íf usíng. Spread evenly ín the líned pan.
5. Bake untíl a toothpíck plunged ínto the center emerges slíghtly moíst wíth batter, 20 to 25 mínutes ís Medrích’s suggestíon but ít took me at least 10 mínutes longer to get them set. Let cool completely on a rack. (í go further and throw míne ín the frídge or freezer for a whíle; ít’s the only way í can get them to cut wíth clean línes.)
6. Líft up the ends of the parchment or foíl líner, and transfer the browníes to a cuttíng board. Cut ínto 16 or 25 squares.

Source: https://smittenkitchen.com/2010/01/best-cocoa-brownies/