In a bowl, cream together the butter and caster sugar until smooth.

Mix in the egg yolk and salt.

Add the flour and mix until a soft dough forms.

Press the dough evenly into the lined tin. Bake for 20-25 minutes, or until lightly golden, and let it cool completely.

In a saucepan over medium-low heat, add butter, light brown sugar, salt, condensed milk, and golden syrup.

Stir continuously until the butter melts and sugar dissolves (stirring is important). Increase to medium heat and cook, stirring constantly, for 5-6 minutes until thickened and deep golden.

Pour over the cooled crust and spread evenly. Chill for 1-2 hours, until set.

Heat the cream and chocolate together using the double boiler method and stir until smooth and glossy.

Pour over the chilled caramel and spread evenly. Chill for at least 2 hours (or overnight for clean slices).

Let sit at room temperature for 10-15 minutes before slicing for that perfect ooey gooey texture.