Melt the butter in the microwave. In a large bowl combine the granola, peanut butter, vanilla extract, butter and salt, and mix with your hands to combine thoroughly.

Line a baking sheet with parchment paper. Spoon the granola mixture onto the baking sheet, to cover in a layer ½ to ¾in thick. Cover with another sheet of parchment paper and press evenly with a weight (such as a cookbook) to compact and flatten.

Place the baking sheet in the fridge for 1 hour. Remove, cut into bars, enjoy! Should keep refrigerated for a while.