Whisk together milk, sour cream, eggs, melted butter, oil, and vanilla.
Add flour, sugar, baking powder, baking soda, and salt directly into the wet ingredients and fold until almost combined.
Fold in blueberries.
For the streusel, mix flour, sugar, and melted butter until crumbly.
Fill muffin liners high, top with some extra blueberries and streusel, and bake at 425°F for 5 minutes, then 350°F for 15–18 minutes until golden.
