Preheat the oven to 180 degrees. Grease and line a traybake tin with parchment paper. Peel and roughly mash the bananas.
Melt the butter in a saucepan and stir in the golden syrup. Mix together the mixed seeds, mashed bananas, rolled oats and dates then add to the saucepan and mix together. Spoon the mixture into the tin and level the surface.
Bake for 30 minutes or until golden brown. Leave the cool before cutting into bars.