Put the vanilla whey protein powder, plain flour, caster sugar, baking powder and fine salt into a large bowl and whisk until smooth with no lumps.
In a separate bowl, whisk the large egg, milk, melted unsalted butter (or a little vegetable oil) and vanilla extract until just combined.
Pour the wet ingredients into the dry ingredients and gently stir with a spatula until the streaks of flour disappear – a few small lumps are fine.
Heat a non-stick frying pan or griddle over a medium-low heat and lightly grease with a little butter or oil.
Spoon or pour about 60 ml of batter per pancake onto the hot pan. Cook for 2–3 minutes, until bubbles form on the surface and the edges look set.
Carefully flip the pancakes and cook for a further 1–2 minutes, until golden and cooked through.
Transfer the cooked pancakes to a plate and keep warm. Repeat with the remaining batter, greasing the pan lightly between batches, then serve warm.