Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners and set it aside.
Mix the Dry Ingredients for the Batter:
In a medium bowl whisk together the flour, baking powder, baking soda, and salt.
Cream the Wet Ingredients:
In the bowl of a stand mixer, beat the softened butter, oil, and sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition.
With the mixer on low, slowly incorporate the sour cream and vanilla. Gradually add the dry ingredients, mixing just until combined. Avoid overmixing to keep the batter light and airy. Give the mixture one final stir by hand to ensure everything is evenly blended.
Make the Streusel:
In a medium bowl, whisk together the flour, sugar, and cinnamon. Using a fork or a pastry cutter, work the butter into the mixture until crumbly.
Spoon the batter evenly into the prepared muffin cups, filling each about 3/4 full. Sprinkle the streusel generously over the top of each muffin.
Bake for 15–20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Serve warm or at room temperature with your favorite coffee or tea.