Prepare Oven and Muffin Pan: Preheat your oven to 400°F (204°C). Line your muffin tin with paper liners—use 8 for large muffins, 10 for standard-sized, or 22 for mini muffins. Lightly grease the muffin pan tops with a small amount of oil or nonstick spray to help prevent the muffin crowns from sticking, especially if you’re making larger muffins.
Combine Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until thoroughly blended. This even distribution ensures your muffins will rise properly and have balanced sweetness.
Mix Wet Ingredients: In a separate measuring cup or medium bowl, pour in the vegetable oil, then crack the egg into the oil. Add milk until the total liquid reaches about 1 cup in volume (roughly ⅓ cup milk in addition to oil and egg). Stir in the vanilla extract, whisking gently until the mixture is smooth and uniform.
Bring Wet and Dry Together: Pour the wet ingredients into the bowl with the dry ingredients. Using a spatula or large spoon, gently fold everything together just until the flour is moistened. Avoid overmixing—the batter should be thick and lumpy, not smooth or runny, to keep the muffins tender.
Fold in Blueberries: Carefully fold the blueberries into the batter, ensuring they are evenly distributed but without crushing them. If you’re using frozen blueberries, add them directly from the freezer to keep the batter from turning blue.
Portion Batter into Muffin Cups: Scoop the batter evenly into the prepared muffin cups. For bakery-style tall muffins, fill the cups almost to the top. Sprinkle each muffin with a little extra granulated sugar to add a delicate, crunchy crust.
Bake to Perfection: Place the muffin pan in the preheated oven and bake. Standard or large muffins take 15–20 minutes; mini muffins require less time, about 9–11 minutes. Check for doneness by inserting a toothpick into the center—if it comes out with moist crumbs but no raw batter, they’re ready.
Cool and Enjoy: Remove the muffins from the oven and transfer them to a cooling rack. Let them cool slightly before serving to fully develop their flavors and texture.