¼ cup (57 grams) unsalted butter2 tablespoons (24 grams) granulated sugar*2 tablespoons (28 grams) firmly packed light brown sugar*1 large egg yolk (19 grams)1 tablespoon (15 grams) whole milk½ teaspoon (2 grams) vanilla extract½ cup (63 grams) all-purpose flour½ teaspoon (2.5 grams) baking powder¼ teaspoon kosher salt¼ cup (43 grams) chopped 60% cacao bittersweet chocolate2 tablespoons (14 grams) chopped pecans*Garnish: flaked sea salt
Preheat oven to 350°F (180°C).
In a small saucepan, melt butter over medium heat; cook, stirring occasionally, until butter turns golden brown and has a nutty aroma, 5 to 6 minutes. Remove from heat; let cool for 5 to 10 minutes.
In a medium bowl, whisk together browned butter, sugars, egg yolk, milk, and vanilla until combined. Stir in flour, baking powder, and kosher salt just until dry ingredients are moistened. Stir in chocolate and pecans.
Lightly spray a 6-inch cast-iron skillet with baking spray with flour. Spread dough into prepared pan.
Bake until edges are golden brown and center is just set, 15 to 20 minutes. Let cool on a wire rack for 20 minutes. Garnish with sea salt, if desired. Serve warm.