Filipino Caramel Cake

Method

1. Heat the oven to 165°C (145°C fan). Line the bases of two 20 cm round metal cake pans, at least 5 cm deep, with baking paper; leave their sides ungreased so the chiffon can grip. Separate the eggs carefully into clean bowls. No yolk or grease should enter the whites.
2. Whisk cake flour, baking powder, cake salt and the 60 g portion of cake sugar. In another bowl whisk the four yolks, cake milk, oil and cake vanilla, then combine with the dry ingredients to make a smooth batter. Do not beat for an extended time once smooth.
3. Whip the whites with cream of tartar until foamy. Add the remaining 90 g cake sugar gradually while beating to glossy medium-firm peaks: the tip should just bend, without dry clumps. Stir a quarter of the whites into the yolk batter, then fold in the remainder in two additions without crushing the foam.
4. Divide the batter evenly between the pans. Bake for 25–32 minutes, until the centres spring back and a skewer has no wet batter. Cool the shallow layers in their pans on a rack, not stacked, for about 30 minutes; loosen the sides, remove the paper and finish cooling completely. Handle these layers gently.
5. For the icing, mix 60 ml cold icing milk, cornstarch and the extra yolk until completely smooth. Warm the other 240 ml milk separately until steaming. Have it ready before starting the caramel. Use a high-sided heavy saucepan and keep hands and face away from the pan when liquid is added.
6. Heat the 140 g icing sugar with 35 ml water over medium heat. Swirl instead of stirring after it boils. When amber, not dark brown or smoking, remove from the heat. Add the warm milk a little at a time; it will bubble fiercely. Return to low heat and stir until any hardened caramel dissolves.
7. Whisk a few spoonfuls of the hot caramel milk into the yolk slurry, then whisk the slurry back into the saucepan. Cook over medium-low heat, whisking across the base and corners, until thick bubbles break the surface; continue for 1 minute. Off the heat, stir in the butter, icing vanilla and pinch of salt.
8. Spread the icing in a shallow heatproof bowl, cover its surface and cool until thick enough to hold a soft ridge, about 30–40 minutes. Refrigerate as necessary rather than leaving the milk icing warm for hours. If it becomes too firm, loosen with a teaspoon of milk and whisk; do not pour hot icing over chiffon.
9. Place one completely cool cake layer on a plate. Spread with about one-third of the icing, add the second layer and coat the top and sides with the remainder. Chill 45–60 minutes to steady the layers. A thin, smooth coating is the intended finish; no buttercream decorations are required.
10. Slice with a clean warm knife, wiping between cuts. Refrigerate covered at 4°C or below for up to 3 days; let individual slices stand about 15 minutes before eating. Do not leave the whole milk-iced cake unrefrigerated beyond 2 hours, or 1 hour in heat above 32°C.