Place your fresh blueberries on a plate or sheet pan in the freezer overnight, or for at least an hour, before starting the rest of your batter.
Heat oven to 400°F and line a large sheet pan with parchment paper or aluminum foil (spray foil with nonstick spray)
Melt butter and allow to come to room temperature while you mix your batter.
In a small mixing bowl, whisk together your dry ingredients. Set aside.
In a large bowl, combine Greek yogurt, eggs, and vanilla extract. Whisk together completely.
Add the dry ingredients to the wet ingredients, using a rubber spatula to mix halfway. It will be very dry and shaggy looking.
Continue mixing while you drizzle in your melted and cooled butter. This is a very thick batter.
Gently fold in the frozen blueberries until evenly dispersed in the batter.
Using a medium scoop, or a couple spoons, make twelve mounds of muffin dough on your prepared baking sheet.
Top with sparkling or granulated sugar, if desired.
Bake in preheated oven for 18 to 20 minutes, or until golden brown and risen well.
Check for doneness by inserting a skewer or toothpick into the center of a muffin top. If it comes out clean, or with just a few crumbs, it is done.
While the muffin tops are baking, whisk together the powdered sugar, milk or lemon juice, and vanilla in a small bowl.
Allow muffin tops to cool for about 10 minutes, then drizzle generously with your glaze.