Preheat a fan forced oven to 150 degrees Celsius.
Slice Granny Smith apples into slices half a centimeter thick. Place apples in a saucepan with 1 tbs water and stew on low for 6-8 minutes or until soft. Set aside to cool.
In a clean bowl, beat egg yolks with sugar until the mixture turns pale yellow.
Add vanilla essence, salt and melted butter. Whisk until combined.
Sift flour into the mix and whisk gently until combined. Add milk slowly and whisk until it resembles a pouring cream consistency.
In a separate clean bowl, whisk egg whites until stiff peaks form. Gently fold egg whites into the egg yolk and milk mixture.
Grease a 20cm x 30cm springform baking tin with, or line with baking paper. Lay the apple slices on the bottom of the tin. Pour the mixture over the apple slices.
Bake for 40-45 minutes. Remove from the oven and leave to cool for 30 minutes.
Serve warm with custard or a dollop of cream.
