Line the base and sides of a 20cm square cake tin with baking paper, make sure you leave plenty of paper hanging over the sides to help your remove it later.
Crush the biscuits until they resemble fine breadcrumbs, you can use either a food processor of the end of a rolling pin!
Place the butter, chocolate and golden syrup into a microwave safe bowl and cook for 30 second spurts until all the ingredients have melted. Stir well to combine.
Set aside approximately 20 Maltesers to decorate.
Pour the melted ingredients into a bowl with the biscuit crumbs and add the rest of the Maltesers. Stir with a large metal spoon to combine.
Pour the mixture into your prepared baking tin and push down with the back of a spoon to flatten the surface.
Break the white chocolate into squares and place it into a microwave safe bowl. Cook for 30 second spurts until it's almost melted and stir until it has completely melted.
Pour the melted white chocolate over the slice and decorate with the reserved Maltesers.
Place the slice in the fridge for 4 + hours to set before cutting into squares.