Preheat oven to 425°F. Line muffin tin with paper muffin liners. In a large mixing bowl, whisk together flour, baking powder, baking soda and salt.
In a separate bowl, whisk together eggs and sugar. To egg mixture, whisk in vegetable oil, butter, vanilla extract and buttermilk.
Pour wet mixture into dry ingredients. Mix until batter forms. Fold in blueberries.
Spoon muffin batter into muffin tin. Batter should be near the top. Bake at 425°F for 17-19 minutes or until tops are golden brown and toothpick inserted into the center comes out clean. Remove from heat and let cool for 5 minutes in pan. Remove to wire rack to finish cooling.
Notes
Frozen blueberries may increase cooking time by 2-4 minutes. Recipe was tested using Bulgarian Style Whole Milk Buttermilk.