Preheat the oven to 300 degrees F (150 degrees C).
Combine egg whites, espresso, vanilla extract, and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment. Beat until egg whites begin to form soft peaks, about 2 minutes. Slowly mix in sugar and stevia powder. Continue to beat until meringue becomes glossy and stiff peaks form.
Gently fold cocoa powder, cacao nibs, and coffee grounds into the meringue. Drop spoonfuls of the mixture onto an ungreased baking sheet.
Bake in the preheated oven until tops start to turn golden and crispy, about 30 minutes.