Combine Dry Ingredients: In a large bowl, whisk together the plain flour, baking powder, bicarbonate of soda, caster sugar, and salt. Set aside.

Mix the Wet Base: In a separate medium bowl, whisk the three egg yolks until they are pale and slightly frothy. Add the ricotta cheese, whole milk, vanilla extract, and lemon zest (if using). Whisk until the mixture is smooth and well combined. Don't worry if there are a few tiny lumps of ricotta.

Combine Wet and Dry: Pour the wet ricotta mixture into the bowl with the dry ingredients. Gently fold them together with a spatula until just combined. Be careful not to overmix; a few small lumps of flour are perfectly fine.

Whip the Egg Whites: In a clean, dry bowl (preferably glass or metal), use an electric hand mixer or a stand mixer with the whisk attachment to beat the three egg whites on medium-high speed. Beat until they form stiff, glossy peaks. This should take about 3-4 minutes.

Fold in the Egg Whites: Take about a third of the whipped egg whites and stir them into the batter to lighten it up. Then, add the remaining egg whites and gently fold them in using a large spatula. I find that a figure-of-eight motion works best for me. Continue folding just until no large streaks of egg white remain. The batter should be thick and airy.

Cook the Pancakes: Heat a large non-stick frying pan or griddle over a medium-low heat. Add a small knob of butter or a little oil. Once the butter is melted and sizzling, drop spoonfuls of batter (about 60ml or ¼ cup each) onto the pan, leaving space between them.

Flip and Finish: Cook for 2-3 minutes on the first side, until you see bubbles forming on the surface and the edges look set. Gently flip the pancakes and cook for another 1-2 minutes on the other side, until they are golden brown and cooked through.

Keep Warm and Serve: Transfer the cooked pancakes to a plate and keep them warm in a low oven (around 100°C) while you cook the remaining batter. Serve immediately with your favourite toppings.