Preheat your oven to 375°F (190°C) to ensure even baking and a golden crust.
Grease your muffin tin with butter or line it with paper liners for easy removal.
In a large mixing bowl, whisk together the all-purpose flour, baking powder, salt, nutmeg, and all-spice.
In another bowl, cream together the unsalted butter, granulated sugar, and light brown sugar until light and fluffy.
Beat in the eggs one at a time, then add the vanilla extract and mix until combined.
Stir in the sour cream and whole milk until smooth and creamy.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined to avoid dense muffins.
Gently fold in the blueberries, using them fresh or frozen without thawing.
Spoon the batter into the muffin tin cups about 3/4 full to allow room for rising.
Bake for 18-22 minutes until a toothpick inserted comes out clean and tops are golden brown.
Let muffins cool in the tin for a few minutes, then transfer to a cooling rack before serving.