Preheat oven to 375 degrees F.
In a medium sized bowl combine flour, baking powder, and salt. Set to the side.
In a large mixing bowl, combine room temperature butter and sugar, and cream by hand or using an electric mixer until it reaches a pale yellow color, about 5 minutes. Add in oil, eggs, and vanilla and stir to combine. Add milk and stir again.
Add in dry ingredients to the wet ingredients until just combined, but don't over mix.
Add in frozen blueberries (you can coat them in flour first to help stop the color from spreading) by gently folding them in with a silicone spatula.
Scoop 2 tablespoon scoops into each section of your prepared muffin tin. You can use paper liners, silicone muffin cups, or nonstick spray to prevent sticking. Many mini muffin pans are non stick as is.
Bake for 15-17 minutes, or until lightly golden brown on the outside. A toothpick should pull away cleanly (or just be dyed blue if you hit a blueberry).
Once cool enough to handle, transfer to a cooling rack and enjoy.