Preheat oven to 425F. Line a 12-cup muffin tin with muffin liners and set aside.
In a large bowl, beat butter and sugar until smooth and creamy. Beat in eggs, yogurt, buttermilk, and vanilla until smooth.
In a separate medium bowl, combine 2 cups flour, baking powder, baking soda, and salt. Fold into liquid mixture until batter is just combined. In a small bowl, toss blueberries with remaining 1 tablespoon flour and fold into batter.
Fill prepared muffin cups halfway full of batter. Set aside for a moment.
Cream Cheese Filling
In a medium bowl, beat cream cheese, egg yolk, sugar, and vanilla until smooth and creamy.
Divide cream cheese filling between muffin cups and top with remaining muffin batter, filling cups to brim with batter.
Bake muffins at 425F 5 minutes, then reduce heat to 350F and continue baking an additional 15-20 minutes until muffins are golden brown and spring back when lightly touched.
Cool muffins 20 minutes in pan, then transfer to a wire cooling rack to cool completely. Enjoy!
Notes
Storing InstructionsStore muffins in refrigerator up to 4 days.