Preheat oven to 350ºF. Grease a muffin tin, standard sized or mini, and set aside.
Combine all the ingredients except the dark chocolate in your Blendtec blender and blend on high until smooth and completely combined. Stir in the chopped chocolate by hand (it would be pulverized by the blender otherwise).
Evenly distribute the batter amongst the prepared muffin cups (6 standard sized or 18 mini). Bake in the oven at 350ºF for 8-10 minutes, or until a toothpick inserted in the center comes out clean. Let the muffins cool for 10 minutes until firm. The remove from the tin and let cool completely on wire racks. These gems are best served fresh and warm, but they should keep in the fridge for about 5 days. Devour.