Preheat oven to 350 degrees F. and line 12 muffin cups with liners (foil liners recommended). If using paper liners, spray liners lightly with cooking spray before filling with batter. You can also spray your muffin tin generously with cooking spray if you prefer to not use liners. I've done both options.
In a large mixing bowl, beat sour cream, eggs and vanilla until well combined. Stir in pumpkin and cinnamon. Slowly add flour, sugar, baking soda and salt, stirring until well combined. Fill liners 1/2 full with batter.
To prepare streusel topping cut cold butter into small cubes and place into medium mixing bowl. Add flour and sugars. Using a pastry cutter or fork, cut butter into ingredients until well combined and butter in small pieces. Top evenly over each muffin cup.
Bake for 25-28 minutes, or until baked though. Remove and let cool. Serve room temperature or chilled.