Heat oven to 375°F. Line muffin tins with baking cups or grease well with cooking spray.
In a large bowl, whisk together the sugar, butter, oil, eggs, and vanilla until smooth. Add the milk and whisk again until combined.
¼ cup (57g) salted butter, ¼ cup (57g) vegetable or canola oil, ¾ cup (150g) granulated sugar, 2 large eggs, 1 teaspoon vanilla extract, ¾ cup milk
In another bowl, whisk together the flour, baking powder, and salt. Add the dry ingredients to the wet ingredients, then stir by hand with a spatula or wooden spoon just until evenly moistened. It's okay for a few streaks of flour to remain.
2 cups (250g) all-purpose flour, 2 teaspoons baking powder, ½ teaspoon salt
Toss the blueberries with 2 teaspoons of additional flour to help prevent them from sinking, then gently fold them into the muffin batter. If using frozen blueberries, do not defrost them before adding them to the batter. Let the batter rest for 15 minutes.
2 cups blueberries
Fill each baking cup about ¾ full, then sprinkle a few extra blueberries on the top of each muffin, if desired. For more rounded domes, use two muffin pans, alternating muffin cups to provide more space around each muffin while baking to help them rise better.
⅔ cup (83g) all-purpose flour, ⅓ cup (66g) granulated sugar, ⅛ teaspoon salt, ¼ cup (57g) salted butter
Make the streusel by mixing the butter, flour, sugar, and salt in a medium bowl, then divide evenly among the muffins, and sprinkle about 1 tablespoon on the top of the muffin batter before baking.
Bake for 22-25 minutes, until done. Cool for 5-10 minutes before transferring to a wire rack to cool completely.