Step 1

Cut 10 tablespoons vegan butter into 10 pieces. Place in the bowl of a stand mixer (or large bowl if using an electric hand mixer) and let sit at room temperature until softened, about 1 hour.

Step 2

Break 3 ounces vegan dark chocolate into large pieces with your hands and place on a cutting board. Chop into pieces no larger than 1/2 inch (about 2/3 cup). If using walnuts, chop 1/2 cup toasted walnuts into pieces the same size.

Step 3

Sift 1 2/3 cups all-purpose flour, 1/3 cup Dutch-processed cocoa powder, 1 1/2 teaspoons baking powder, and 1/4 teaspoon instant espresso powder if using into a medium bowl. Add 1/2 teaspoon kosher salt and whisk to combine.

Step 4

Add 2/3 cup packed light brown sugar and 1/3 cup granulated sugar to the vegan butter. Beat with the paddle attachment on medium speed until creamy, about 2 minutes. Scrape down the sides of the bowl with a rubber spatula. Add 1/4 cup unsweetened non-dairy milk and 1 1/2 teaspoons vanilla extract and beat until well-combined (it will look curdled), about 1 minute.

Step 5

Add the flour mixture and mix on low speed just until most of the flour is incorporated. Add the chopped chocolate, walnuts, 2/3 cup semi-sweet chocolate chips, and 1/4 cup cocoa nibs if using. Scrape down the sides of the bowl with the spatula and mix by hand just until combined. The dough will be thick and sticky like chocolate frosting.

Step 6

Cover the bowl with plastic wrap or a silicone lid and refrigerate for at least 30 minutes or up to 24 hours.

Step 7

Arrange 2 racks to divide the oven into thirds and heat the oven to 375ºF. Line 2 baking sheets with parchment paper or silicone baking mats.

Step 8

Scoop the dough out in 2-tablespoon portions or with a #30 cookie scoop (about 1 1/4 ounces or 34 grams each). Roll each portion into a ball with your hands. Place on the baking sheets, spacing them at least 2 inches apart, 9 per baking sheet. Flatten each ball slightly with your hand until a scant 2 inches wide. Sprinkle the cookies with a little flaky salt. Refrigerate any remaining cookie dough.

Step 9

Bake for 5 minutes. Rotate the baking sheets between racks and from front to back. Bake until the cookies have spread, are set around the edges, and the centers are no longer shiny, 4 to 7 minutes more (do not overbake so you get a chewy, almost brownie-like texture).

Step 10

Let the cookies cool on the baking sheets for 5 minutes. Transfer to a wire rack and let cool completely. Repeat baking the remaining cookie dough on a cooled baking sheet (you can reuse the parchment or mat).