Pre-heat the oven to 375 degrees.
In a bowl, mix the dry ingredients together (sifted flour, baking powder, and salt).
In a bowl, mix the butter, oil, and sugar. Add the vanilla, eggs, and milk and whisk until combined.
Slowly add the sifted flour mixture into the bowl of the liquid mixture and fold. Add all the flour into the wet mixture until it is well combined. There should be no streaks or lumps of flour in the muffin batter.
Toss your washed blueberries in a tablespoon of flour. Make sure they are all lightly coated. The flour will prevent the blueberries from sinking.
Gently fold the blueberries into the muffin batter.
Place liners in the muffin tin. Using an ice cream scoop, distribute the muffin batter evenly.
For the crumb topping, mix together the melted butter, flour, sugar, and salt with a fork. Break it up into smaller chunks. Top the blueberry muffin batter with the crumb topping.
Place the muffin tin in the oven and bake for 22-25 minutes.
Remove the muffins from the oven once they are baked. Let the muffins rest for at least 15 minutes before serving.