Pre-Heat oven to 400F (205 C) and prepare a popover tin by placing a small piece of butter into each mold.
In a medium bowl, combine all ingredients except blueberries. Hand whisk together enough to lightly incorporate flour.
Transfer batter to a blender and then mix until smooth.
Once oven is has preheated, place the popover pan with the pieces of butter onto the middle rack. Let the butter melt and pan heat for 2 minutes. Carefully remove from the oven.
Fill the cups ¾ full with the batter. Then, evenly divide the blueberries amongst the molds by gently dropping them on top.
Place pan bake on the center oven rack and bake for 18 minutes (popovers should have puffed). Then, reduce the heat to 350 F (180 C) and bake an additional 18-20 minutes until the popovers are risen, puffed and nicely golden brown on the edges.
Carefully remove the pan from the oven.
Gently lift popovers from their mold and place on a serving dish. Pierce the center with a fork to release some steam and prevent sogginess. Add a light dusting of confectioner sugar on top and enjoy immediately!