Place racks in upper and lower thirds of oven, preheat 375°F

Whisk 200g flour, 2g salt, 4g baking soda in small bowl; set aside

Cook 1 stick butter in large saucepan over medium heat, swirling and scraping down sides with rubber spatula, until butter foams and browns (about 4 min)

Transfer butter to large bowl and let cool 1 minute

Cut remaining ½ stick butter into quarters and add to brown butter one at a time until melted

Add both (200g, packed, brown; 50g granulate) sugars and whisk, breaking up clumps until incorporated

Add egg and yolks and whisk until sugar dissolves and mixture is smooth

Whisk in 2 tsp vanilla

Using rubber spatula, fold reserved dry ingredients into butter mixture until no dry spots remain

Fold in 170g chocolate, 2 Tbsp cocoa powder

Dough should be soft but hold shape; if it slumps or oozes, stir back together and let rest 5-10 min until scoops hold their shape

Using a 3 Tbsp scoop, portion 16 balls and divide between 2 parchment-lined rimmed baking sheets

Bake, rotating sheets if unevenly browning, until deep golden brown and firm around edge, 8-10 min

Let cool on sheegs

Keeps for 3 days; store airtight at room temp