In a small bowl stir the cream cheese and sugar until smooth.
The Yummy Topping
With a fork, combine the melted butter, sugar, and flour in a small bowl. (keep some of the larger chunks!)
The Muffin Batter
Preheat the oven to 350°F. Line muffin pan with paper muffin cups or spray with Pam.
In an electric mixer, mix eggs until frothy (2 minutes). Add sugar and vegetable oil, mix until smooth. Add vanilla, vinegar, baking soda, and salt, mix thoroughly. Add sour cream, gently and briefly mix. Add flour.
Thoroughly clean the blueberries. Stir blueberries into batter mixture with a spoon. (Keep some out to place on top of batter in the muffin pan.)
Fill muffin cups ⅔ of the way.
Add Cream Cheese filling to the muffin batter using a spoon. Place it in the center of the muffin batter, carefully fold it into the center.
Sprinkle 1-2 spoonfuls of the crumble topping on top of the muffin batter and pat it down gently.
Baking
Bake for 15-20 minutes for normal muffins and 25-30 minutes for large muffins. Double check by putting a toothpick in the muffin, if it comes out clean the muffin is ready!
Storing
Eat within 3-4 days.
I encourage you to freeze some as well! They last frozen for about a month. (Microwave and they're ready to eat!)