1. Preheat your oven to 350 degrees F (175 degrees C). Place paper liners into a muffin tin and set the tin aside.

For the Streusel

1. Get a medium bowl. Add the dry streusel ingredients which are the flour, sugar, and cinnamon. Stir them together using a whisk to mix everything well.
2. Now add the cut pieces of cold butter into the dry mix. Use a fork or a pastry cutter to work the butter into the mixture. Keep mixing until the butter is fully combined and the mixture looks crumbly. Set this streusel mix to the side for later.

For the Batter

1. In a different medium bowl, measure out the flour, baking powder, baking soda, and salt. Whisk these dry ingredients together until they are well combined. Set this bowl aside for now.
2. Use the bowl of your stand mixer. Add the softened butter, oil, and sugar. Beat these together until they are well blended and creamy.
3. Add the eggs one at a time. Make sure to mix well after each egg is added to the bowl.
4. Keep the mixer running on a low speed. Slowly add the sour cream and the vanilla extract. Mix these in. Next, add the flour mixture that you prepared earlier. Continue mixing just until everything is fully combined. Be careful not to mix too much.
5. Once the mixer is turned off, use a spatula. Give the batter one final stir by hand. This makes sure any wet ingredients stuck at the bottom are mixed into the flour completely.

Assembly

1. Take the prepared muffin tin. Spoon a heaping tablespoon of the batter into the bottom of each paper cup.
2. Sprinkle some of the streusel mixture you made earlier evenly over the layer of batter in each cup.
3. Divide the rest of the batter among the muffin cups. Spoon this second layer of batter directly on top of the streusel layer.
4. Finally, divide the remaining streusel topping. Sprinkle it generously over the top of the batter in each muffin cup.

Baking

1. Place the filled muffin tin into the preheated oven. Bake for about 15 to 20 minutes.
2. The muffins are done when a toothpick inserted into the center of one comes out clean with no wet batter attached.
3. Carefully remove the pan from the oven. Let the muffins sit in the tin for a few minutes before lifting each one out.
4. Transfer the baked muffins to a wire rack. Let them cool completely on the rack.