Whisk buttermilk, milk, eggs, and butter together in a large bowl. *short the milk and adjust after combining if needed.
Combine flour, sugar, baking powder, baking soda, and salt in a bowl; stir into buttermilk mixture just until blended. Adjust batter thickness to your liking by adding more flour or buttermilk.
Heat a large skillet over medium heat; coat with cooking spray. Drop batter by ¼ cupfuls onto the skillet; cook until bubbles appear on the surface. Flip and cook until browned on the other side. Repeat with remaining batter.
