In a large mixing bowl, whisk together the all-purpose flour, vanilla whey protein powder, baking powder, and salt.
Add the milk, eggs, melted butter, and vanilla extract if using.
Whisk just until combined. Do not overmix. If the batter is too thick, add 1 to 2 tablespoons extra milk.
Heat a nonstick skillet or griddle over medium heat. Lightly grease if needed.
Pour about 1/4 cup of batter into the skillet for each pancake.
Cook for 2 to 3 minutes, until bubbles form on the surface and the edges look set.
Flip and cook for 1 to 2 minutes more, until the second side is golden and the pancake is cooked through.
Repeat with the remaining batter.
Serve warm with strawberries, maple syrup, yogurt, nut butter, or your favorite toppings.