Prepare the puree. Grind the currants with a blender. Put the currant puree on low heat, bring to a boil, cook for 7-10 minutes. Rub the puree through a sieve to remove the seeds and peel. Cut the apples into cubes, cook them in boiling water for 10 minutes until they become soft. Grind the apples with a blender, add to the currants. Pour in the sugar, stir until completely dissolved. Cook the puree for 5 minutes.
Cook the syrup. Pour water into a saucepan, add sugar and agar-agar. Bring to a boil, cook for 5-6 minutes. Stir vigorously, preventing the syrup from sticking to the bottom. Pour the syrup into the puree, beat for 2 minutes.
Prepare the marshmallow mixture. Add the egg whites to the puree and beat with a mixer at maximum speed until stiff peaks form. Pour the syrup in a thin stream and continue beating until the mixture doubles in size. The process may take 10 minutes.
Form the marshmallow. Transfer the mixture into a pastry bag, pipe the marshmallow halves onto a parchment-lined tray. Leave the marshmallow to dry for 10 hours on the table at room temperature.