Step 1

Preheat your oven to 350 F.

Step 2

Line an 8×8 inch metal pan or 9×13-inch metal pan with parchment paper (please read the Notes & Tips section above if using a 9×13-inch metal pan OR a glass pan). I like to grease the pan first so the parchment paper lays flat. Brownie batter is thick and has a tendency to “pull up” the paper when spreading the batter into the pan.

Step 3

Melt the semi-sweet chocolate chips and butter in a double boiler; set aside.

Step 4

Meanwhile, in a stand mixer fitted with the whisk attachment: combine the granulated sugar, brown sugar, eggs, vanilla, salt (and instant espresso granules, if using) Whisk vigorously on medium speed until voluminous and pale in color, about 5-7 minutes. This step dissolves the sugar which is crucial for crinkle-top brownies.

Step 5

With the mixer running: pour in the warm, melted chocolate mixture.

Step 6

Add the sourdough starter and mix to combine.

Step 7

Add the cocoa powder, flour and baking soda.

Step 8

Fold in semi-sweet chocolate chips (optional) and mix well to combine.

Step 9

Pour the batter into the lined pan. Tap the pan on the counter a few times to release any air bubbles.

Step 10

Bake on the center rack for 35-40 minutes (8×8-inch metal pan) OR 30 minutes (9×13-inch metal pan) or until the top is set. A toothpick won’t come out perfectly clean when pressed into the center; you’ll get some crumbs and fudge batter. The finished brownies will be more baked around the outer edges and fudgy in the middle. The texture will continue to set as the brownies cool.

Step 11

Remove from the oven and allow the brownies to cool completely in the pan (they become fudgier as they sit). Don’t rush this step. Hot brownies taste very different than cool brownies. Be patient.

Step 12

Cut into slices and enjoy!