Sour Cream Coffee Cake Muffins

I made these muffins this weekend and halved the recipe.  They turned out well.  By accident, for the topping I halved the butter but not the flour or sugar.  All were eaten:)

For the streusel
• ½ cup all-purpose flour
• ½ cup granulated sugar
• 1 teaspoon ground cinnamon
• 6 tablespoons unsalted butter, cut into ½ inch pieces
For the batter
• 2 ¼ cups all-purpose flour
• 2 teaspoons baking powder
• ½ teaspoon baking soda
• ¼ teaspoon salt
• 1/3 cup unsalted butter, softened to room temperature
• 1/3 cup vegetable or canola oil
• 1 cup granulated sugar
• 2 large eggs
• 1 cup sour cream
• 2 teaspoons vanilla extract

Instructions

1. Preheat oven to 350 degrees. Line a muffin tin with paper liners and set aside.
2. In a medium bowl, add the dry streusel ingredients (flour, sugar and cinnamon) and stir with a whisk to combine. Using a fork or a pastry cutter, add the butter pieces and work into the dry mixture until well incorporated. Set aside.
3. To make the batter, in another medium bowl, add the flour, baking powder, baking soda and salt and whisk together. Set aside.
4. In the bowl of stand mixer, beat together softened butter, oil, and sugar and mix well. Add the eggs one at a time, mixing well after each egg is added.
5. Keeping the mixer on a low speed, slowly add in the sour cream and vanilla and finally the flour mixture and mix until fully combined, but being careful not to over mix the batter. (Once you’ve turned off the mixer, using a spatula, give the mixture one additional stir by hand just to make sure that all of the wet ingredients from the bottom are completely mixed into the flour mixture.)
6. Spoon a heaping tablespoon of batter into each prepared muffin cup. Then sprinkle some of the streusel mixture on top of the batter. Divide the remaining batter into the muffin cups (spoon on top of the streusel layer) and then divide the remaining streusel over each muffin, sprinkling it over the batter.
7. Bake for 15-20 minutes or until a toothpick inserted into the center of the muffin comes out clean.
8. Remove the pan from the oven and remove each muffin to a wire rack to cool completely.