Preheat oven to 350* and fill a 12-muffin pan with paper liners
In a medium bowl, add your dry streusel ingredients together. Then, using a fork or pastry cutter, cut the butter into the dry streusel ingredients until the mixture in crumbly. Set aside bowl
In another medium mixing bowl, beat together your butter, oil, and sugar until combined. Add in your eggs and mix well until just smooth.
Next, carefully mix in your sour cream and vanilla, beating just til combined
To the batter, slowly add in your dry ingredients (flour, baking powder, baking soda, and salt). Mix well until all dry ingredients are combined and batter is smooth. Batter will be thick.
Spoon a rounded tablespoon of batter into the bottom of each muffin cup, then a spoonful of streusel, followed by another rounded tablespoon of batter and topped with remaining streusel on top. Be careful to divide both layers of batter and streusel equally amongst each muffin cup.
Bake in 350* oven on middle rack for approx 15-20 minutes, depending on oven, or until toothpick inserted in middle comes out clean.
Remove from pan and cool completely on wire rack. ENJOY! :)
