1. Preheat the oven to 180°C/160°C fan and line a 20cm square shallow baking tin with non-stick baking paper.
Mix all the ingredients together (except the seeds), then mash it well with a fork to completely break up the bananas. Once everything is well mixed, scoop it into the baking tin and level the top. Sprinkle the mixed seeds on top (leave off or grind if serving to babies and young children).
2. Bake for 50–55 minutes, until the top is golden and crisp. Once cooked, remove from the tin using the baking paper and leave to cool on a rack until either warm or cooled to room temperature.
3. Slice into 24 small squares, or 12 larger bars to serve. The bars will keep in an airtight container for up to 3 days, or can be wrapped in cling film/beeswax and frozen individually, then defrosted on the counter overnight ready for the morning.
You can also reheat them uncovered in a microwave for 30 seconds if you’d like them warm.