Activate the buttermilk effect: In a measuring jug, combine the lukewarm milk and fresh lemon juice. Give it a quick stir and set aside for 5-10 minutes. You will see the mixture begin to curdle slightly and thicken, which is exactly what we want. This mimics buttermilk, adding tenderness and a subtle tang.

Whisk the dry ingredients: In a large bowl, sift together the plain flour, caster sugar, baking powder, bicarbonate of soda, and fine sea salt. Whisk briefly to ensure everything is evenly distributed. The sifting aerates the flour, which contributes to a lighter waffle.

Combine the wet ingredients: In a separate bowl, whisk the egg yolks with the vanilla extract. Pour in the thickened milk mixture and the vegetable oil (or melted butter), whisking until smooth. The mixture will look pale and slightly emulsified.

Make a well and combine: Create a well in the centre of the dry ingredients. Pour the wet mixture into the well. Using a wooden spoon or a rubber spatula, stir gently from the centre outwards, just until the flour is moistened. A few small lumps are perfectly fine; over-mixing will develop the gluten and make the waffles tough. The batter should be thick but pourable, the texture of a thick milkshake.

Whip the egg whites to stiff peaks: In a clean, grease-free bowl, whisk the egg whites with an electric mixer on medium-high speed until they hold stiff, glossy peaks. When you lift the whisk, the peak should stand straight up without flopping over. This process should take about 3-4 minutes and will sound like a soft, steady hum.

Fold in the egg whites: Take a large spoonful of the whipped egg whites and stir it into the batter to lighten it. Then, gently fold the remaining whites into the batter using a figure-eight motion with your spatula. Fold just until no white streaks remain. The batter will now be very airy, almost mousse-like in its lightness.

Rest the batter (crucial step): Cover the bowl with a clean tea towel and let the batter rest at room temperature for at least 1 hour. During this time, the flour hydrates fully, and the gluten relaxes, which ensures a tender interior and a crispier exterior. The surface might develop a few small bubbles, which is a good sign.

Preheat your waffle iron: About 10 minutes before the batter is ready, preheat your waffle iron to a medium-high setting. A drop of water should sizzle and dance on the surface.

Cook the waffles: Give the rested batter a gentle, quick stir (it will have deflated slightly). Lightly brush the waffle iron grids with a little melted butter or oil. Pour the recommended amount of batter onto the centre of the iron (usually about ¾ cup, depending on your machine). Close the lid and cook until the waffle is deep golden brown and crisp, and steam stops escaping from the sides. This usually takes 4-5 minutes. The sound will change from a loud sizzle to a quieter, steady hiss as it finishes cooking.

Keep warm and serve: Transfer the cooked waffle to a wire rack set inside a baking tray and keep it warm in a low oven (about 100°C) while you cook the remaining batter. This prevents them from steaming and becoming soggy.