For the Cupcakes:

1. Preheat oven to 350° F.
2. Combine vanilla cupcake mix with vanilla pudding. Add egg whites, one at a time, beating well after each egg is added to ensure it is well mixed.
3. Add buttermilk, oil, sour cream and vanilla. Beat on medium speed until all ingredients are well combined. Use a spatula to scrap down the side of the bowl and turn the batter over from the bottom.
4. Line a cupcake pan with paper liners.

For the Streusel:

1. Combine all dry ingredients in a medium-sized bowl.
2. In a separate bowl, melt butter. Pour melted butter over dry ingredients. Use a spoon to blend butter into dry ingredients to create a crumbly mixture.
3. Spoon a little bit of batter into the bottom of the cupcake. Pour a teaspoon or two of streusel on top of the batter and swirl with a toothpick. Spoon remaining batter into cupcake liner till it is about 2/3 full. Pour a teaspoon of streusel on top.
4. Bake at 350°F for 15-18 minutes until the cupcakes are done. You do not want to top to turn brown. Check for doneness by inserting a toothpick in the middle of the cupcake. If the toothpick comes out clean, your cupcakes are done. Allow them to cool completely.

For the Frosting:

1. Beat butter in mixer on medium speed until smooth and creamy: 2-3 minutes.
2. Add brown sugar and mix until combined.
3. Slowly add powdered sugar 1 cup at a time while continuing to beat on medium speed. After 3 cups of powdered sugar, the frosting might be very thick and crumbly. Add 1 tablespoon of heavy cream and the vanilla extract and beat into the frosting before adding additional powdered sugar.
4. Continue to add the remaining powdered sugar and the cinnamon and mix into the frosting. Alternate in the heavy cream as needed.
5. Increase the mixer speed to high to whip frosting until smooth and creamy. Frost cooled cupcakes.