Preheat oven to 375°
Prepare muffin tin with paper liners or grease with shortening and flour as you would a cake pan.
Make streusel topping by combining flour, sugar, and cinnamon in a medium bowl. Add butter and mix with a fork until the topping is crumbly. Set aside.
Add blueberries to a sifter fitted to a large bowl. Sift flour over blueberries. Pour flour coated blueberries into a separate bowl.
Finish sifting baking powder, salt, and nutmeg into the bowl with the flour. Whisk to combine. Set aside.
In a separate bowl, whisk eggs and sugar until combined. Add sour cream, oil, and vanilla extract. Whisk until well combined.
Add wet ingredients to flour mixture. Stir to lightly combine. Stir in blueberries.
Spoon batter into muffin tin, filling 2/3 full. Cover generously with streusel topping. Lighlty press topping into each muffin.
Bake for 20 - 25 minutes or until a steak knife inserted in the center comes out clean.
Let pan cool on cooling rack until the pan is cool enough to handle. Remove muffins and allow to cool on rack until ready to serve.
