Stir yeast and 1 tablespoon of sugar until the yeast becomes liquid. Warm the milk lukewarm. Knead 500 g flour, 1 pinch of salt, 50 g sugar, milk and yeast with the dough hooks of the mixer, kneading 75 g soft butter in flakes until the dough is smooth.
If it forms a ball, continue kneading for about 3 minutes. Cover and leave to rise in a warm place for about 1 hour.
Wash the currants and drain well. Strip the berries from the panicles with a fork. Mix the Double cream, vanilla sauce powder and 30 g sugar.
Briefly knead the yeast dough on some flour. Roll out to a rectangle (approx. 35 x 50 cm). Spread vanilla cream on top, leaving a rim of about 2 cm all around. Sprinkle with berries.
Roll up the dough from the short side. Cut into about 16 slices. Place on two baking trays lined with baking paper. Cover and leave to rise in a warm place for about 45 minutes.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Coarsely chop the marzipan and knead it with 4 tbsp. flour, 30 g butter in pieces and 1 pinch of salt to form crumbles. Sprinkle on the snails.
Bake in a hot oven for about 25 minutes each time. Stir icing sugar and 2 tablespoons of water until smooth. Take out snails and immediately sprinkle with the icing. Let them cool down.