Knead butter, flour, sugar and egg into a shortcrust pastry and press firmly in a 26cm springform pan. Form an approx. 3-4 cm high edge. Prick several times with a fork and chill for 30 minutes.
Mix the pudding powder with a little of the milk until smooth, bring the remaining milk and sugar to the boil and add the pudding mixture while stirring vigorously. Remove the saucepan from the heat and stir in the sour cream.
Finally, carefully fold in the currants.
Bake in the preheated oven at 175 ° for approx. 60 minutes. (If necessary, cover halfway through the baking time so that it does not get too dark!)
After baking, let cool in the pan.
Bring the cake topping with 250 ml cassis juice to the boil while stirring and spread on the cheesecake.