Peel and remove the core from the apples before cutting into 1/2cm slices.

In a large shallow pan, pour the sugar in with the apples and cook on a medium heat.

Cut the skin off the Florida Grapefruits, then slice the segments out before adding to the apples.

Add a pinch of salt to help improve the flavour, I promise it works!

To make the crumble, break the California walnuts up in your hand and place in a mixing bowl.

Add the flour, oats and butter to the bowl along with the sugar and mix together with your hands to make a crumble.

Finally for the crumble add an egg yolk and stir together.

Mix the corn flour with a little water to make a thin paste.

When the apples are soft and cooked, pour the cornflour in and stir together.

The apple and Florida Grapefruit mixture will thicken as you stir together, remove from the heat and pour into an ovenproof dish ready for the crumble.

Scatter the crumble mixture over the apples and grapefruit and gently spread out.

Bake in the oven at 170c for 30-40 minutes, until golden.