Preheat your oven to 400°F / 200°C.
Grease a 12-cup muffin tin or line it with paper cups.
In a large bowl, whisk together the dry : flour, sugar, baking powder, and salt.
In a separate medium bowl, beat the egg, then whisk in the milk and melted butter or oil until just combined.
Pour the wet into the center of the dry .
Using a spatula, fold everything together until just moistened.
Do not overmix—the batter should be lumpy and thick.
Carefully spoon the batter into the prepared muffin cups, filling them about two-thirds full.
Bake for 20 to 25 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean.
Let the muffins rest in the tin for 5 minutes before transferring them to a wire rack to cool slightly.
Serve warm and enjoy!
Do not overmix! A lumpy, just-combined batter is the secret to a tender, fluffy muffin. Overmixing develops gluten and makes them tough.