Combine Dry Ingredients: In a large mixing bowl, whisk together the plain flour, baking powder, bicarbonate of soda, caster sugar, and salt. Mixing them now ensures everything is evenly distributed.

Mix the Wet Ingredients: In a separate medium bowl or jug, whisk the egg yolk with the buttermilk, melted butter, and vanilla extract until just combined.

Create the Batter: Pour the wet ingredients into the bowl with the dry ingredients. Whisk them together until they are *just* combined. It’s very important not to overmix; a few lumps in the batter are perfectly fine and actually desirable.

Rest the Batter: Let the batter sit at room temperature for 5-10 minutes. This allows the gluten to relax and the flour to absorb the liquid, which leads to more tender pancakes.

Whip the Egg White: While the batter rests, place the egg white in a clean, dry bowl. Using an electric hand mixer or a stand mixer, whisk the egg white until it forms soft peaks. You should be able to lift the whisk and see a peak that softly curls over on itself.

Fold in the Egg White: Take a large metal spoon or spatula and gently fold the whipped egg white into the batter in two additions. I find a figure-of-eight motion works best to incorporate it without knocking out all the air you just created. The batter should look light and moussey.

Heat Your Pan: Place a large non-stick frying pan or griddle over a medium-low heat. Add a small knob of butter and let it melt and foam.

Cook the Pancakes: Ladle about 2-3 tablespoons of batter per pancake into the hot pan, leaving space between them. Cook for 2-3 minutes, or until you see bubbles appearing on the surface and the edges look set.

Flip and Finish: Carefully flip the pancakes with a thin spatula and cook for another 1-2 minutes on the other side, until they are golden brown and cooked through.

Keep Warm and Repeat: Transfer the cooked pancakes to a baking tray in a low oven (around 100°C) to keep warm while you cook the remaining batter, adding a little more butter to the pan for each batch.