In a large bowl, combine the flour, sugar, baking powder, baking soda, and salt.
2 cups all-purpose flour, 2 tablespoons granulated sugar, 1½ teaspoons baking powder, ½ teaspoon baking soda, ¼ teaspoon kosher salt
In a separate bowl, whisk the buttermilk, milk, eggs, butter, and vanilla together.
2 cups buttermilk, 1 large egg, 2 tablespoons unsalted butter, 1 teaspoon pure vanilla extract
Pour the wet ingredients into the dry ingredients, then use a wooden spoon or rubber spatula to mix until it's just blended together. Let the batter rest for 15 minutes.
Set a large non-stick skillet over medium heat, or heat a griddle to 350°F.
Spray the griddle with cooking spray, then use a ladle or ice cream scoop to pour ¼-½ cup of the batter onto the cooking surface. Cook for 1-2 minutes, until bubbles appear on the surface.
Use a spatula to flip the pancakes and cook until browned on the other side.
Remove the pancake to a plate and repeat with the remaining batter.