Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper. In a large bowl, whisk together the almond flour, cocoa powder, granulated sweetener, chocolate whey protein powder, baking powder, and salt.

In a separate bowl, whisk together the egg, melted butter, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix until just combined. Gradually add the heavy cream, 1 tablespoon at a time, until the batter is thick but still spoonable.

Drop spoonfuls of batter onto the prepared baking sheet, leaving about 2 inches between each. Slightly flatten each mound.

Bake for 10-12 minutes, or until the edges are set and the centers are slightly soft. Let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

Once cooled, spread your favorite keto peanut butter filling (not included in this recipe's ingredients but essential for whoopie pies!) on the flat side of half the cookies. Top with the remaining cookies to form whoopie pies.

Serve immediately or refrigerate for later enjoyment.