Heat the heavy cream in a small saucepan. Meanwhile in a separate pan, mix the sugar and 1/4 cup water and bring to a boil. Once the sugar starts to turn amber, swirl the pan to evenly distribute the color. Remove from the heat and pour in the hot heavy cream, whisking to combine.
Pour the caramel over the chocolate chips and whisk until the chocolate melts, then stir in the butter. Pour the mixture into a shallow dish and chill in the fridge until completely set, at least 45 minutes.
Once set, use a teaspoon to scoop out spoonfuls of the mixture. Roll in your hands until round and roll in cocoa powder to coat.