Grease and line a 20 x 10 cm (8 x 4 inch) loaf tin with non-stick parchment paper. Make sure to leave a couple inches of paper overhanging the sides for easy removal. Set aside.
In a food processor, blend the softened dates, butter, peanut butter, vanilla, and salt until super smooth. Scrape down the sides of the processor in between blends.
Add the rolled oats and pulse 6-8 times until the oats are slightly broken down and everything is well combined.
Tip the mixture into the prepared loaf tin and press it down very, very firmly to compact it into a bar. Chill the bar in the fridge for a minimum of 2 hours.
Once it’s chilled, loosen the edges of the bar with a knife and then pop it out of the tin using the parchment. Slice the bars into 6 equal sized flapjacks. Drizzle with the optional melted chocolate.