• Set the oven to 180℃ (160℃ fan, 350℉, Gas 4).

Base

• Whisk the flour, sugar, coconut and salt together in a large bowl.
  150 g wholemeal flour (whole wheat), 50 g desiccated coconut, 75 g golden caster sugar, 1 pinch fine sea or rock salt
• Add the melted butter and egg yolk and stir until combined.
  100 g unsalted butter, 1 large egg yolk
• Transfer the mix to a 20cm (8 inch) square baking tin or silicone mould. If using a tin, you might prefer to line it with baking paper first with two of the ends hanging over the sides so you can remove the slice easily when needed.
• Press the mix down hard with the back of a spoon and make sure you have a more or less even layer that covers the whole base.
• Bake on the middle shelf of your oven for 10-15 minutes or until lightly golden in colour.

Topping

• Whilst the base is baking, whisk the sugar, salt and egg white together until you can no longer feel any gritty bits from the sugar. It's fine to use the same bowl you used for the base.
  75 g golden caster sugar, 1 pinch fine sea or rock salt, 1 large egg white
• Stir in the desiccated coconut.
  50-75 g desiccated coconut
• As soon as you take the base out of the oven, spread the jam over the top. It's easier to do if the base is still warm. Try to leave a small gap around the edges, so that the jam doesn't stick when you're trying to remove the slice later.
  240 g jam of your choice
• Drop spoonfuls of the coconut topping over the jam and spread it out to cover.
• Bake for a further 15-20 minutes until the top is crisp and golden.
• Transfer the tin to a wire rack and leave to cool completely.
• Once cool, remove the slice onto a bread board using the paper overhangs, then slice into 12 pieces. If using a silicone mould, slice directly in the mould and remove each slice with a spatula.