Preheat oven to 400°F and line a muffin tin with paper liners.
In a large bowl, whisk together the melted butter, sugar, eggs, Greek yogurt (or sour cream), milk, and vanilla.
In a separate bowl, whisk the soft white wheat flour, baking powder, baking soda, and salt.
Add the dry ingredients to the wet ingredients. Stir gently until just combined. Some small lumps are normal — do not overmix.
Let the batter rest for 10–15 minutes. This allows the fresh-milled flour to hydrate and helps the muffins bake up softer.
Right before baking, gently fold in the frozen blueberries. For even distribution and less color bleed, toss the blueberries in a small spoonful of flour before stirring them into the batter.
Scoop the batter into the lined muffin tin, filling each cup generously.
Bake for 15–18 minutes, or until a toothpick inserted in the center comes out clean.
Cool slightly before serving.