from Dorie Greenspan (original description online at cookbookhabit)
1 1/4 cups all-purpose flour 1/3 cup unsweetened cocoa powder 1/2 teaspoon baking soda 1 stick plus 3 tablespoons (11 tablespoons) unsalted butter, at room temperature 2/3 cup (packed) light brown sugar 1/4 cup sugar 1/2 teaspoon fleur de sel or 1/4 teaspoon fine sea salt 1 teaspoon vanilla extract 5 ounces bittersweet chocolate, chopped into chips, or a generous 3/4 cup store-bought mini chocolate chips Cream butter and sugars, salt, and vanilla and beat for 2 minutes. Mix in dry ingredients until just mixed; add chocolate chips.
Roll dough into logs 1 1/2" in diameter. Refrigerate or freeze, then slice into 1/2" thick rounds. Bake for 12 minutes at 325.
Makes about 36 cookies.