01 -
Preheat oven to 350°F (175°C). Line a standard muffin tin with paper liners and set aside.
02 -
In a medium bowl, whisk together the flour, sugar, and cinnamon. Add the butter pieces and incorporate using a fork or pastry blender until the mixture forms coarse crumbs. Set aside.
03 -
In a separate medium bowl, whisk the flour, baking powder, baking soda, and salt together. Set aside.
04 -
In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter, oil, and granulated sugar together until smooth and creamy.
05 -
Add the eggs one at a time, beating well after each addition to ensure thorough integration.
06 -
Reduce mixer speed to low. Pour in sour cream and vanilla extract, mixing until just combined.
07 -
Gradually add the dry flour mixture to the wet ingredients. Mix until just combined, being careful not to overwork the batter. Finish by stirring by hand with a spatula to ensure all ingredients are incorporated from the bottom.
08 -
Spoon a generous tablespoon of batter into each muffin cup. Sprinkle a portion of the streusel over the batter. Divide remaining batter among the cups, then top each with the rest of the streusel, distributing evenly.
09 -
Bake in the preheated oven for 15 to 20 minutes, or until a toothpick inserted into the center of a muffin emerges clean.
10 -
Transfer the muffin tin from the oven and carefully remove each muffin onto a wire rack to cool completely before serving.