I had 3 large sweet and sour apples. Grate the peeled apples on a coarse grater.
Add sugar to the apples, heat almost to a boil, then reduce the heat to a minimum and cook for another 30 minutes, stirring occasionally.
Gelatin pre-fill with water and leave to swell for 20 minutes. Then heat it until it dissolves, I just put it in a bowl of hot water.
Dissolve the starch in cold water.
Add the starch to the Apple mass, bring to a boil, allow to cool slightly and punch with a blender until smooth.
Add gelatin to the mass, mix well.
Put the Apple mass in a mold, I have a silicone one, put it in the refrigerator for stabilization for 3-4 hours, or better at night. The size of my form is 21 x 10 cm. If your form is not silicone, then cover it with food wrap.
When the marmalade is frozen, carefully remove from the mold, cut into portions and serve.