In a medium saucepan, combine the peanut butter, maple syrup (or honey), salt and vanilla extract. Heat over low heat, stirring until the mixture is smooth and well combined.

Remove the saucepan from the heat and stir in the rolled oats until fully incorporated. If you’re using chocolate chips, fold them in at this stage.

Line a loaf pan or an 8x8-inch (20x20 cm) baking dish with parchment paper, leaving some overhang for easy removal. Pour the peanut butter mixture into the prepared dish, pressing it down firmly with a spatula to create an even layer.

If desired, sprinkle the chopped peanuts, more chocolate chips or even flaky salt on top and gently press them into the mixture.

Refrigerate the bars for at least 1-2 hours, or until they’re firm enough to cut. Once set, lift the bars out of the dish using the parchment paper and cut them into squares or rectangles.

Store the bars in an airtight container in the fridge for up to a week, or in the freezer for longer storage.