Preheat the oven to 450 F (230 C). Place 1 teaspoon of butter (5 gr) in each popover cup (make 6). If using a regular muffin pan, just add ½ teaspoon in each (make 12). Place the pan in the oven for 3 minutes to melt the butter and heat the pan.
In your blender, add the flour, maple syrup, eggs, vanilla extract, salt, and milk. Blend well for 1 or 2 minutes. You can also place the ingredients in a large bowl and whisk until light and frothy.
Brush the melted butter all over the inside of the popover cups. Pour the batter to fill each cup to about ¾ of the way. Place about 8 to 10 blueberries in each popover cup.
Bake at 450F (230C) for 15 minutes. Without opening the oven door, lower to 350F (180C) and bake for about 15 more minutes or until puffed and golden brown on top. For regular muffin size: bake 15 to 18 minutes at 450F.
Sprinkle with powdered sugar and serve warm with whipped cream.
