Preheat the oven to 200°C (400°F) and position a rack in the center for even heat circulation. Line a 16-cup muffin tin with paper liners or grease lightly with oil or butter. Proper pan preparation ensures clean release and encourages uniform muffin rise.

In a large mixing bowl, whisk together the all-purpose flour, white sugar, baking powder, and salt until evenly combined. This step distributes the leavening agent uniformly so every muffin rises at the same rate and develops a consistent crumb structure.

In a measuring jug or medium bowl, whisk together the vegetable oil and eggs until smooth and emulsified. Add enough milk to reach a total liquid volume of about 320 ml, then mix until fully combined. Proper emulsification improves moisture distribution and prevents greasy pockets in the finished muffins.

Pour the wet mixture into the dry ingredients and fold together using a spatula or wooden spoon just until no dry streaks remain. The batter should look slightly lumpy and thick. Overmixing activates gluten and leads to dense, rubbery muffins instead of soft, bakery-style texture.

Add the fresh blueberries and white chocolate chips and fold carefully to distribute them evenly without crushing the berries. Gentle handling prevents color bleeding and keeps fruit pockets intact for juicy bursts in the final bake.

In a small bowl, combine sugar, flour, cubed cold butter, and a pinch of salt. Using fingertips or a fork, rub the mixture until coarse crumbs form. The topping should hold together loosely when pressed but still feel sandy and uneven — this texture creates a golden crunchy finish.

Divide the batter evenly among the muffin cups, filling each almost to the top to encourage tall domed muffins. Sprinkle a generous layer of crumb topping over each portion, pressing very lightly so it adheres during baking.

Bake for 20–25 minutes until the tops are deeply golden and a toothpick inserted into the center comes out clean or with a few moist crumbs. Rotate the pan halfway through baking if your oven has hot spots.

Let muffins rest in the pan for 5 minutes, then transfer to a wire rack to cool completely. This short resting period allows structure to set while preventing steam buildup that can soften the crumb topping.