Prepare the oven and tin. Preheat your oven to 160°C (140°C fan). Grease a 23x33cm baking tray and line the base with parchment paper. The tray should be shallow to allow the milk to soak evenly.

Whisk the dry ingredients. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside. You want a uniform, pale beige colour with no lumps.

Whip the egg whites. In a clean, grease-free bowl, beat the egg whites on medium speed until frothy. Gradually add 200g of the caster sugar, one tablespoon at a time, and increase the speed to high. Whip until the mixture holds stiff, glossy peaks. When you lift the whisk, the peak should stand straight up without flopping—this is your visual cue.

Make the yolk base. In a separate large bowl, beat the egg yolks with the remaining 100g of caster sugar until thick, pale, and creamy—this takes about 3-4 minutes. The mixture should fall from the beaters in a thick ribbon that holds its shape on the surface for a second before disappearing. Beat in the milk and vanilla.

Fold everything together. Gently fold the flour mixture into the yolk mixture until just combined. The batter will be thick and slightly lumpy. Now, take a large spoonful of the whipped egg whites and stir it vigorously into the batter to loosen it. Then, gently fold the remaining whites in with a spatula, using a cutting and lifting motion, until no white streaks remain. The final batter should be light, airy, and billowy.

Bake the sponge. Pour the batter into the prepared tin and spread it evenly. Bake for 25-30 minutes, until the top is golden brown and the centre springs back when lightly touched. A skewer inserted into the middle should come out clean. The kitchen will smell toasty and sweet. Cool the cake in the tin on a wire rack for 15 minutes, then run a knife around the edges and turn it out onto the rack to cool completely.

Prepare the three-milk soak. In a large jug, whisk together the sweetened condensed milk, evaporated milk, and double cream until smooth. The mixture will be thick, pale, and slightly glossy.

Soak the cake. Once the cake is completely cool, return it to the baking tin. Poke holes all over the surface with a skewer or fork—about 60-70 holes. Slowly pour the milk mixture over the entire cake, starting at the edges and working your way to the centre. You want to hear a gentle sizzle as the milk hits the sponge. Cover the tin with cling film and refrigerate for at least 4 hours, or preferably overnight. The cake will absorb almost all the liquid, becoming incredibly tender and moist.

Whip the topping. Just before serving, pour the double cream, icing sugar, and vanilla into a chilled bowl. Whip on medium-high speed until the cream holds soft, billowy peaks that are stiff enough to spread but still luscious. You should see the trails from the whisk clearly holding their shape.

Assemble and present. Spread the whipped cream over the soaked cake in gentle, sweeping swirls. Use the back of a spoon to create dramatic peaks and valleys. Dust generously with ground cinnamon. For a restaurant touch, chill the cake for another 30 minutes to set the cream, then slice cleanly with a hot, dry knife.