Cover frozen currants with 0.5 cup water and bring to the boil under a lid. Remove from fire and pass through a sieve; preserve the juice. Pour the remaining marc into 1 liter boiling water, add sugar and cook for 10 minutes. Strain through a sieve and bring to the boil. Dilute starch in 1 cup drinking cold water and slowly pour into the boiling liquid, stirring constantly so that no lumps form. Add currant juice and cook for 2 minutes without boiling, otherwise the kissel will be liquid. Pour the kissel into cups or jelly glasses and cool for 30 minutes.