250g/9oz Bramley apples, peeled, cored and thinly sliced
250g/9oz Cox’s apples, peeled, cored and thinly sliced
a little grated unwaxed lemon zest, to taste
1 tbsp caster sugar
pinch of ground cloves
6–7 slices white bread, about 5mm/¼in thick, crusts removed
120²µ/4½´Ç³ú butter, plus extra for greasing
1 egg yolk