Clean 2 pounds apples, peel off their skins, and remove the cores. Cut the apples into cubes about ½-1 inch in size.
Put the cubed apples in a pot and cover them with a half of 2 cups water. Increase the heat, cover with a lid, and bring to a boil. Then, reduce the heat to low and let the apples simmer for 15 minutes.
Add ¼ teaspoon ground cinnamon, 4 Tablespoons granulated sugar, ½ teaspoon vanilla paste, and 2 Tablespoons lemon juice to the cooked apples. Stir well to combine.
Pour the rest of water into a bowl and add a ladleful of the cooking juices from the apples. Stir in 2 sachets Dr. Oetker vanilla pudding powder and whisk well to ensure there are no lumps in the mixture.
Slowly pour the pudding powder mixture over the cooked apples. Stir thoroughly and bring to a boil over medium heat. The pudding powder will thicken the apples. Cook for about a minute, then remove the pan of apple jelly from the heat.
Crush the apple pieces slightly using a potato masher or another appropriate kitchen tool. Do not blend the mixture; you should still see small chunks of apple in it.
Grab a round springform cake pan with a diameter of 9-10 inches. Line the bottom with baking paper, fit the sides, and trim the excess paper around the perimeter with scissors. You can grease the baking paper on the bottom with a little solid fat.
Prepare 7 ounces sponge biscuits. Place a layer of biscuits on the bottom of the springform pan, arranging them closely together.
Scoop the apple jelly with a ladle and spread it over the biscuits, smoothing the surface as you go.
Place another layer of biscuits on top of the apple jelly.
In a clean bowl, mix 1 ½ cups sour cream with 2 Tablespoons granulated sugar. Pour the cream mixture over the biscuits and spread it evenly. Use a rubber spatula to scrape the sides and bottom of the bowl to make the most of the cream.
Now put the cake in the fridge and leave it there overnight. This will allow the flavors to develop and the biscuits to soften as they soak up the juices from the apple jelly.