Whisk the dry ingredients: In a large bowl, sift together the plain flour, caster sugar, baking powder, bicarbonate of soda, and salt. Whisk gently to combine — the mixture should look pale and uniform, with no lumps of flour visible.

Combine the wet ingredients (minus egg whites): In a separate jug, whisk together the buttermilk, egg yolks, melted butter, and vanilla extract until smooth and fully emulsified. The mixture will be a pale, creamy yellow and smell rich and buttery.

Whip the egg whites: In a clean, dry bowl (preferably metal or glass), use a hand mixer or stand mixer to whisk the egg whites on medium speed until stiff peaks form. You'll know they're ready when you lift the whisk and the peaks stand upright without collapsing — the whites should look glossy and feel firm to the touch.

Combine wet and dry: Pour the wet mixture into the dry ingredients and stir gently with a wooden spoon or spatula until just combined. Do not overmix — a few small lumps are perfectly fine. The batter should look thick and slightly shaggy, with no streaks of dry flour remaining.

Fold in the egg whites: Gently fold the whipped egg whites into the batter in three additions, using a rubber spatula. Cut through the centre of the batter, scrape the bottom, and fold over the top — repeat until just incorporated. The batter will become airy, light, and voluminous, almost like a mousse in texture. Stop folding as soon as no white streaks remain.

Preheat the pan and cook: Place a large non-stick frying pan or griddle over medium-low heat. Add a small knob of butter and swirl to coat the surface. Once the butter has melted and is gently sizzling (but not browning), pour approximately 60ml (¼ cup) of batter per pancake onto the pan, leaving space between each one. Cook for 2-3 minutes, until bubbles appear on the surface and the edges look set and slightly dry. The underside should be a deep golden brown — lift a corner gently to check.

Flip and finish: Flip the pancake carefully with a thin spatula and cook for another 1-2 minutes, until the second side is also golden brown and the pancake feels springy to the touch. Transfer to a wire rack or a warm plate while you cook the remaining batter. Repeat with the rest of the batter, adding a little more butter to the pan between batches if needed.

Rest and serve: Allow the pancakes to rest for 1-2 minutes before serving — this helps the internal steam settle, resulting in a more tender crumb. Stack them neatly on a warm plate, garnish as desired, and serve immediately.