In a large skillet, melt 2 tablespoons of butter over medium heat. Add 4 peeled and cored Bramley cooking apples and 2 chopped Russet eating apples. Sprinkle with 100g caster sugar, cooking for 10-15 minutes until the Bramley apples break down and the Russet pieces become fork-tender.

Once the apples are cooked, drain any excess liquid and stir in the zest of 1 lemon, then set this mixture aside to cool slightly.

In a mixing bowl, beat 4 egg yolks, then gradually add 500ml of whole milk, whisking until combined. In a saucepan, melt 2 tablespoons of butter over medium heat, then add 40g of plain flour to form a paste. Gradually stir in the yolk-milk mixture and cook until thickened, about 10 minutes. Add 1 teaspoon of vanilla bean paste.

Preheat your oven to 180°C (350°F). Spread the apple mixture evenly in a baking dish and pour the custard over the apples, leveling it gently with a spatula.

Sprinkle demerara sugar and ground cinnamon evenly over the custard layer. Place under a preheated grill for about 5 minutes, being careful not to burn.

Remove from the oven and let rest for 15 minutes before serving warm, optionally with vanilla ice cream or whipped cream.