In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk together the buttermilk, milk, egg, and melted butter.
Pour the wet ingredients into the dry ingredients and gently stir until just combined. Do not overmix; it's okay if there are a few lumps.
Preheat a griddle or non-stick skillet over medium heat. Lightly coat with cooking spray or butter.
Pour 1/4 cup of batter onto the griddle for each pancake. Cook until bubbles form on the surface of the pancake and the edges begin to look set.
Flip the pancake and cook the other side until golden brown.
Remove the pancakes from the griddle and keep warm. Repeat with the remaining batter.
Serve the pancakes warm with your favorite toppings, such as maple syrup, fruit, or whipped cream.