• Preheat the oven to 350°F.
• Spray a jumbo muffin pan with non-stick cooking spray or use jumbo cupcake liners.

Streusel Filling and Topping

• Whisk brown sugar, sugar, cinnamon and pecans together. Set aside ¾ cup for the filling.
• Add flour, butter and vanilla to the remaining mixture and form a crumbly streusel like topping.

Coffee Cake Muffins

• In a small bowl, gently mix egg yolks, 6 tablespoons of sour cream and vanilla. Set aside.
• In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
• Add butter and remaining sour cream. Mix until well combined.
• Gradually add egg mixture slowly, a little at a time. Mix well after each time. Batter will be thick and sticky.
• Add batter half way, to each muffin liner, followed by 2 tablespoons of filling, one tablespoon of blueberries, and more batter. Top with streusel topping.
• Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
• Set on a cooling rack to cool.