Pre-heat the oven to 300ºF (150ºC) and line a 8x8 baking tray with grease-proof paper.  Beat the butter and sugar until light and fluffy. Add the flour and mix until a dough forms. Push the dough out into the prepared pan, prick all over with a fork and then bake for around 15 minutes, just until the edges are browned (the rest of the base will be very pale and bubbling). Leave to cool and harden slightly. Turn the oven up to 350ºF (175ºC).

Heat the condensed milk and sugar together on a medium heat for around 15 minutes (until the colour darkens and the mixture thickens). Remove from the heat, stir in the peanuts and pour over the crust.

While the base is cooking, prepare the topping. Melt the butter and then add to the flour, sugar and salted peanuts. Stir until evenly mixed. Using your fingers, crumble the topping and sprinkle all over the top of the caramel.  Bake for a further 15 minutes until the topping is starting to brown. Remove, allow to cool completely and then slice into small bits. Enjoy!