Blitz oats and almonds in a food processor until finely ground. Transfer to a large bowl and mix in the remaining base ingredients. Press evenly into the prepared tin.
Melt the chocolate in the microwave in 10-second bursts until smooth. Stir in the peanut butter and pour over the base. Tap the tin gently to remove air bubbles.
Refrigerate for 1-2 hours until firm.
Slice into bars and enjoy. Store in the fridge in a sealed container for 1-2 weeks.
