Heat the oven to 180C/fan 160C/gas 4 and line 2 baking trays with baking paper.
In a large bowl, whisk the egg into the sugar until fully combined. Add the vanilla and salt, and stir to combine with a wooden spoon. Mix in the peanut butter until well combined and a dough forms. Leaveto stand for 5-10 minutes to firm up.
Form the dough into 12 balls and spread evenly across the baking trays. Press lightly to flatten them slightly and sprinkle over a little extra salt and chopped peanuts.
Bake for 10-13 minutes or until golden brown. Transfer to a wire rack to cool for 10 minutes before eating. These can be stored in a tin for up to 3 days or frozen for up to 2 months.
*This recipe is gluten-free according to industry standards