Ingredients:
1 cup(226 grams) unsalted butter, any temperature
1 cup(170 grams) bittersweet chocolate
1 cup(114 grams) plump dried cranberries
3/4 cup(150 grams) dark brown sugar
3/4 cup(150 grams) granulated sugar
1 teaspoonvanilla extract
1 large egg
1 large egg yolk
1 1/2 teaspoonsbaking powder
1 teaspoonkosher salt
3/4 teaspoonbaking soda
1 1/2 cups(180 grams) rye flour
1 cup(120 grams) all-purpose flour
1/4 cup(28 grams) cornstarch
1/3 cup(40 grams) cacao nibs
Flaky sea salt
Vanilla ice cream, heavy cream, or crème fraîche, for serving (optional)
Directions:
Heat the oven to 375°F. In a 10½-inch cast-iron skillet over medium heat, melt the butter, whisking occasionally. Cook until the butter goes from a pale yellow to a golden brown color and the foam subsides. The brown butter will have a nutty aroma. Remove from the heat and transfer to a large bowl. Let cool for 10 minutes while you gather the other ingredients. Set the greased skillet aside.
Coarsely chop the chocolate and reserve about 1 tablespoon each of chopped chocolate and dried cranberries.
To the bowl with the brown butter, add the brown sugar, granulated sugar, and vanilla and whisk to combine. Whisk in the egg and egg yolk until emulsified. Sprinkle the baking powder, kosher salt, and baking soda over the surface of the batter and mix until very well combined. Add the rye flour, all-purpose flour, and cornstarch and carefully stir with a rubber spatula until the dough just comes together and no streaks of flour remain. Stir in the cacao nibs and remaining cranberries and chopped chocolate until evenly distributed. Scrape the batter into the cast-iron skillet and smooth the top with an offset spatula. Scatter the reserved chopped chocolate and cranberries over the dough.
Bake the cookie, rotating the pan halfway through, for about 20 minutes, until the edges are puffed and golden brown and the center is just set. The center will still be gooey and slightly underbaked. Sprinkle with the sea salt and let sit for 10 to 15 minutes to cool slightly. Serve warm with a scoop of vanilla ice cream, dribble of heavy cream or dollop crème fraîche if using, in the center.