01 - Preheat the oven to 400°F. Grease a muffin tin, ensuring empty spaces between filled cups to prevent sticking.
02 - In the bowl of a stand mixer, combine the butter and 1/2 cup sugar. Beat on high speed until light and creamy.
03 - Add the egg to the creamed mixture and mix on medium speed until fully integrated.
04 - Add all-purpose flour, matcha powder, dry milk powder, baking powder, salt, water, and vanilla extract. Mix on medium speed until uniform.
05 - Crush half of the blueberries and add them to the batter. Mix until evenly distributed.
06 - Add the remaining whole blueberries. Use a silicone spatula to gently fold them into the batter.
07 - Scoop the batter evenly into the prepared muffin tin.
08 - Allow the batter to rest in the tin for 45 minutes at room temperature.
09 - Sprinkle about 1 teaspoon granulated sugar over each portion, covering the surface.
10 - Bake for 20 minutes at 400°F, or until the tops are golden brown and set. Remove and cool before serving.