• Preheat the oven to 350°.
• Line a 12-count muffin tin with paper liners or spray with non-stick cooking spray. Set aside.

Muffins

• Place blueberries in a small bowl and add ¼ cup of flour. Stir to fully coat blueberries and set aside.
• In a large bowl, mix together the egg, buttermilk, oil, vanilla, and sugar.
• Add in the flour, baking powder, and salt. Stir until just combined.
• Fold in the flour covered blueberries.

Cream Cheese Filling

• In a medium mixing bowl, beat the cream cheese until light and fluffy (about 2-3 minutes).
• Add in the egg yolks, sour cream, and sugar.
• Beat until well combined and smooth. Set aside.

Streusel Topping

• In a small bowl, combine the brown sugar, flour, cinnamon, and butter.
• Using a fork, or clean hands, mix the butter in with the dry ingredients until fully incorporated.
• Fill each muffin liner ½ way, add in a tablespoon of cream cheese mixture and use a toothpick to swirl into the batter.
• Add batter on top until about ⅔ full.
• Now, top each muffin with a generous amount of streusel topping and bake in the preheated oven for 18-22 minutes until a toothpick inserted comes out clean.