Simmer blueberries and water in a saucepan over medium heat for 5–7 minutes. Mash with a fork as they heat until reduced to a thick paste. Cool completely before using.
Add all Wet Blend ingredients to a blender. Blend until completely smooth.
In a large bowl, thoroughly whisk together all Dry Mix ingredients until uniformly combined.
Pour the liquid wet blend into the dry mix bowl. Fold gently with a spatula just until the flour disappears. Do not overmix.
Grease a mini muffin tin. Fill only EVERY OTHER WELL to allow space for maximum muffin tops. Spoon batter until each active well is ¾ full.
Drop ½ teaspoon of cooled blueberry paste onto each muffin cup. Use a toothpick to swirl the paste into the batter.
Sprinkle tops with coarse sugar. Bake at 350°F (175°C) for 12 to 15 minutes, or until a toothpick comes out clean.