Place cacao butter over a double boiler to gently melt the chocolate. If using a traditional double boiler, fill the bottom with water and place the top pot over it with the cacao butter already inside. Bring the water to a boil to produce the heat to melt the cacao butter. If you do not have a double boiler, simply fill a small to medium saucepan with water and bring it to a boil. Place a heatproof glass bowl with the cacao butter inside over the boiling water and heat until melted. Stir the chocolate occasionally to ensure an even melt.
Add in the rest of the ingredients except the dark chocolate. Whisk well to combine. There will be a few lumps at the bottom and that is ok. Use powdered sweetener for this application.
Pour the mixture onto a half rimmed baking sheet lined with parchment. Tilt the pan to spread it completely out to all the edges. Place in the fridge for 5-10 minutes or until the top is starting to solidify but still tacky. Shave the dark chocolate using a vegetable peeler onto a piece of parchment. Then sprinkle it over the coffee bark evenly.
Chill until completely firm about 3-4 hours. Break into individual pieces. Keep the bark stored in the fridge or freezer in an airtight container or bag.