Vanilla muffins - Bake When It Rains

In a large bowl, combine the all-purpose flour, baking powder, baking soda and salt. Set aside.
In a medium bowl, whisk together melted butter, granulated sugar, brown sugar, egg, milk, and vanilla.
Pour the butter and egg mixture into the flour mixture and fold together until just combined. Be careful not to overmix to avoid gummy muffins.
Cover and chill the batter for 1 hour. This is optional, but I find that it improves the texture. While the batter is resting, preheat the oven to 425°F and line a muffin tin with 6 muffin cups or paper liners. After 1 hour, the batter will become thicker.
Pour the batter into a muffin pan, splitting even between 6 muffins.
Bake for 10 mins, then lower the oven temperature to 375°F and bake for another 5 mins, or until a toothpick comes out clean.
Let sit in the muffin tin for around 5 minutes so they are easier to take out. Then take out and cool on a wire rack.