Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.

In a large mixing bowl, whisk together the sifted cocoa powder, granulated erythritol, salt, and baking powder until well combined and no cocoa lumps remain.

In a separate bowl, whisk the egg whites and vanilla extract just until frothy and slightly lightened, but not to soft or stiff peaks.

Pour the frothy egg whites into the dry ingredients. Stir with a spatula until a thick, glossy batter forms. If the mixture seems overly stiff or dry, add strong brewed coffee or espresso, 1 teaspoon at a time, just until the batter loosens to a scoopable consistency.

Fold in sugar-free dark chocolate chips and chopped toasted pecans, if using, distributing them evenly without overmixing.

Let the batter rest for 5 minutes to allow the cocoa and sweetener to hydrate and thicken slightly. This helps the cookies hold their shape and reduces spreading.

Using a small cookie scoop or two spoons, drop heaping tablespoon portions of batter onto the prepared baking sheets, spacing them about 2 inches apart. The batter will be glossy and a bit loose but should mound slightly.

Bake, one sheet at a time, for 10–12 minutes, or until the cookies have a shiny, crackly top and the edges are just set but the centers still look slightly soft.

Remove the baking sheet from the oven and let the cookies cool completely on the pan. They will firm up as they cool while staying fudgy in the center.

Once fully cooled, carefully peel the cookies from the parchment. Store in an airtight container at room temperature for up to 4 days, or refrigerate for a firmer, truffle-like texture.