German Chocolate Cake with Coconut-Pecan Filling

Make the coconut-pecan filling. Whisk the evaporated milk, brown sugar and egg yolks together in a heavy saucepan, then add the butter and salt. Cook over medium heat, stirring constantly, for 12-15 minutes until the mixture thickens, turns a deep caramel colour and reaches 80°C. Off the heat, stir in the vanilla, coconut and pecans, then leave to cool to room temperature, stirring occasionally as it thickens to a spreadable consistency. Making the filling first gives it time to cool and set properly before the cake needs it.

Melt the chocolate. Heat the oven to 175°C (155°C fan) for at least 20 minutes and grease and base-line the three 20 cm tins. Stir the chopped chocolate into the boiling water until fully melted, then leave to cool.

Cream the butter. Beat the butter, sugar and salt together for 4 minutes until pale and fluffy. Beat in the egg yolks one at a time, then the vanilla and the cooled melted chocolate. Beating the butter and sugar well at this stage traps air that helps keep the finished cake light despite its rich filling.

Mix in flour and buttermilk. Mix in the flour and bicarbonate of soda in three additions, alternating with the buttermilk in two, mixing only until just combined each time. Whisk the egg whites to stiff peaks and fold them in gently in two additions. Alternating the dry and wet ingredients like this stops the batter from curdling or turning lumpy.

Bake the layers. Divide the batter between the three tins and bake for 25-30 minutes until the sponges spring back when pressed and a skewer comes out clean. Leave the sponges to settle in their tins for 10 minutes, then tip them out onto a wire rack and let them cool fully before you think about filling.

Fill and stack. Stack the three layers with a third of the coconut-pecan filling spread between each one and on top, leaving the sides of the cake bare. Leaving the sides unfrosted is traditional for this cake, showing off the layers of filling as you cut into it.