For the apple-banana jam wash the apples, peel, core and cut into fine pieces. Peel the bananas (rather ripe but not too ripe!) and also cut into fine pieces.
Add 1 kg of jam sugar (the amount is enough because both fruits are starchy) and let it melt slowly on the stove. Blend with a hand blender and simmer for a few minutes.
If the jelly test fits then fill into rinsed jars and screw tightly.