Preheat the oven to 160°C. Grease and line a 20cm square tin with parchment paper.
For the base, blitz the fl our, pretzels, sugar and butter together in a food processor and press into the prepared tin. Prick with a fork and pop into the oven for 25-30 minutes. Allow to cool a little.
For the caramel, add the ingredients into a small saucepan. Whisk to combine over low heat.
Once the butter has melted, increase the heat, continuously stir until everything has melted.
Reduce the heat a little and simmer for 4-5 minutes, stirring constantly until the mix has thickened. It’s ready when you can see it coming away from the pan and coating the back of the spoon.
Pour the caramel over the base and spread to create an even surface. Chill in the fridge for two hours.
Melt the chocolate in a bowl with the butter in a microwave or over a saucepan of simmering water. Let this cool a little.
Once the caramel has set, pour the chocolate over the top and then break up the pretzels a little and sprinkle them over with the sea salt.
Chill until the chocolate has hardened.
To divide into squares, use a knife warmed in hot water to stop the chocolate cracking.