Walnut Cake

Steps

1. 1
   Heat the oven to 175°C and line the base of a 24 cm springform tin with baking paper.
2. 2
   Whisk the eggs and sugar on high speed for 10 minutes, until tripled in volume and thick.
3. 3
   Mix the walnuts, flour and baking powder and fold them in gently with a spatula in three additions — the oil in the nuts knocks out air, so fold lightly and stop as soon as no streaks remain.
4. 4
   Pour into the tin and bake for 35–40 minutes, until a skewer comes out clean. Cool completely, then cut horizontally into three layers.
5. 5
   Boil the water with the sugar for the syrup for 2 minutes, take off the heat, stir in the vanilla and cool.
6. 6
   For the cream, heat 400 ml of the milk until steaming. Melt the caramel sugar in a dry heavy pan over medium heat to a deep amber, take off the heat and pour in the hot milk carefully — it spits and the caramel seizes — then stir over low heat until the caramel dissolves.
7. 7
   Whisk the yolks and cornflour with the remaining 100 ml of milk, whisk in a ladle of the caramel milk, pour it all back into the pan and cook, whisking, until very thick, then 1 minute more. Press cling film onto the surface and cool completely.
8. 8
   Beat the butter for 5 minutes until pale, then beat in the cooled caramel cream a spoonful at a time.
9. 9
   Brush each layer with syrup and stack them with the cream between, then coat the top and sides. Press the ground walnuts for the sides onto the cake, set the walnut halves around the top and chill for at least 4 hours.