Preheat and Prepare the Muffin Tin
Preheat your oven to 400°F (200°C). Line a 12-cup muffin tin with muffin liners or grease with non-stick spray.
Combine Dry Ingredients
In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Mix Wet Ingredients
In a separate bowl, whisk together the oil (or melted butter), egg, vanilla extract, and milk until smooth.
Combine the Batter
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Be careful not to overmix, as this can make the muffins dense.
Fold in the Blueberries
Gently fold in the blueberries with a spatula, distributing them evenly throughout the batter.
Fill Muffin Cups and Add Topping
Divide the batter evenly among the muffin cups, filling each about ¾ full. If desired, sprinkle the tops with a pinch of coarse sugar for a crunchy top.
Bake
Bake in the preheated oven for 18-20 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean. Allow the muffins to cool in the tin for 5 minutes, then transfer them to a wire rack to cool completely.