Wash the blueberries in a colander, then spread them on paper towels to dry. Allow them to dry completely, about 1 hour.
Melt the chocolate chips in a microwave-safe bowl in 30-second sessions, stirring after each session. You’ll likely need 3 sessions to melt it completely.
Stir the avocado oil and the sweetener (if using) into the melted chocolate.
Add the dry blueberries to the melted chocolate. Stir gently with a spoon to ensure they are well coated.
Using the same spoon, transfer clusters of the mixture into a large, wax-paper-lined plate. In total, when using large blueberries and measuring out 6-7 of them per cluster, you should get 8 clusters.
If you have any leftover melted chocolate in the bowl, you can now drizzle some of it on top of each cluster.
Refrigerate the clusters until the chocolate is set, 20-30 minutes. Keep them in the fridge for up to two days, and remove the portion you want to eat from the fridge 30 minutes before enjoying (unless your house is super hot).