Heat the oven to 180C/160C fan/gas 4 and generously oil a 22cm non-stick square brownie tin. Beat the peanut butter, maple syrup and egg whites together using a fork until well combined. Stir in the oats, raisins and pumpkin seeds to make a sticky dough.

Press the dough into the tin in a thin, even layer, then bake for 15-18 mins until golden and firm. Cut into 12 rectangles, then tip out onto a wire rack and leave to cool completely. Will keep in an airtight container for up to a week.