Whisk the dry ingredients. In a medium bowl, whisk flour, cocoa powder, baking powder, baking soda, and salt until even. If using espresso powder, add it here.

Melt and cool the chocolate. Microwave chopped chocolate in 20–30 second bursts, stirring between each. Stir in the melted butter until smooth. Let cool to lukewarm so it doesn’t scramble the eggs.

Beat the sugars and eggs. In a large bowl, whisk granulated sugar, brown sugar, and eggs for about 1–2 minutes until slightly thick and lightened. Mix in vanilla.

Add the chocolate mixture. Pour the melted chocolate-butter mixture into the egg mixture and whisk until glossy and uniform.

Combine wet and dry. Add the dry ingredients and stir with a spatula just until no dry spots remain. Fold in mini chocolate chips if using. The dough will be thick and sticky.

Chill. Cover and refrigerate for at least 2 hours, or up to 24 hours. This step is key for easy rolling and pronounced crinkles.

Prep to bake. Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper. Place the extra granulated sugar in one shallow bowl and the powdered sugar in another.

Shape and coat. Scoop the dough into 1 to 1.5-tablespoon portions. Roll into balls with slightly damp or lightly oiled hands. Roll each ball first in granulated sugar to create a moisture barrier, then generously in powdered sugar. Aim for a thick, even coating.

Arrange and bake. Place balls 2 inches apart on the sheets. Bake 9–11 minutes, until the cookies have spread, the tops are cracked, and edges are just set. They should look slightly underbaked in the center.

Cool. Let cookies rest on the sheet for 5 minutes, then transfer to a rack to cool completely. They’ll firm up as they cool while staying fudgy inside.