These cookies are thick, fudgy, oh-so-deeply chocolatey with a subtle sourdough tang that hits right at the end and makes the chocolate taste even richer.
Place chopped butter, chocolate and espresso powder in a large microwave safe mixing bowl. Use a chocolate melting setting (or 30 second bursts) in the microwave - stir when prompted (or after each burst) until the chocolate and butter are fully melted and smooth. Set aside and let the mixture cool for 5 minutes.
170 g butter, 110 g bittersweet chocolate, 1 g espresso powder
Whisk the brown sugar, sugar, egg, egg yolk and vanilla into the cooled chocolate mixture until the sugars are dissolved and the mixture looks smooth and glossy.
225 g brown sugar, 75 g sugar, 1 egg, 1 egg yolk, 20 g vanilla
Add the flour, sourdough discard, baking powder, salt and cocoa powder into the mixing bowl. Stir until no traces of discard and no dry bits of flour remain.
270 g flour, 84 g sourdough discard, 15 g baking powder, 9 g salt, 38 g cocoa powder
Fold the chocolate chips in until they are evenly distributed. Cover the bowl with plastic wrap and refrigerate the dough for at least 30 minutes to allow the flour to hydrate, flavors to mature and the dough to firm up.
260 g chocolate chips
Preheat the oven to 375°F and line two large baking sheets with parchment paper.
Take the cookie dough out of the refrigerator and portion the cookies out using a firmly packed #30 cookie scoop. Slightly flatten the top of each mound of dough to form a thick disc. Arrange the cookie dough on your prepared baking sheets at least 2 inches apart. If you'd like, press a few extra chocolate chips into the surface of each cookie. Bake for 7-9 minutes or until the edges are set, the center is soft and puffed and the surface looks dry. Avoid overbaking, the cookies should have a soft fudgy texture even after cooling completely.