Refrigerate a can of full fat coconut milk for at least 2 hours. This will cause the coconut cream to separate from the water. The cream will settle at the top of the can while the water will sink to the bottom. Take the can out of the fridge and do not shake it. Carefully open the coconut milk with a can opener. Using a spoon scoop out the heavy cream into a measuring cup.
Place the cream in the microwave and microwave for 1 minute or until the cream just starts to boil.Remove the cream from the microwave and pour it over the chocolate chips and add 1 tablespoon of butter.
Using an offset spatula stir the chocolate until it's completely melted. Place a sheet of parchment paper into a 6 by 4 inch container. Pour the chocolate mixture into the container. Lightly bang the container onto the counter to release any trapped air bubbles.
Place the container in the fridge for 2-5 hours to let the chocolate set. Remove the chocolate from the fridge and peel the parchment paper away from the sides.
Use a knife dipped in warm water to slice the chocolate into squares. Wipe the knife between cuts to ensure clean edges. Dust the top of the chocolate with cocoa powder or powdered sugar for a decorative garnish.