Preheat the oven for the dough (electric oven: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (20 cm Ø) with oil. Mix flour, 200 g sugar, cocoa, baking powder, baking soda and 1⁄4 TL salt in a mixing bowl.
Mix coffee, 80 ml oil and vinegar. Pour into the flour mixture. Stir only briefly until everything is just mixed. Fill into the mould, smooth it down. Bake in a hot oven for about 25 minutes. Take out and let cool down.
For the cream, soak gelatine in cold water. Mix ricotta, 2 tablespoons sugar and vanilla sugar. Squeeze the gelatine gently. Dissolve carefully in a small pot at low heat. Gradually stir 2-3 tbsp. ricotta cream into the gelatine.
Stir the gelatine mixture into the remaining cream. Whip cream until stiff and fold in.
Cut the top of the coffee cake straight. Crumble the cut-off pieces finely. Cut the cake in half horizontally. Place the bottom bottom on a plate. Place the cake ring on top. Spread half the jam on top. 1⁄3 Spread ricotta cream on top.
Sprinkle with chocolate shavings. 1⁄3 Gently pour the cream on top. Spread the cut surface of the upper cake base with the rest of the jam. Place the coated side on the ricotta cream. Spread almost half of the remaining cream on top.
Pour the rest of the cream into a piping bag. Chill the cake for about 30 minutes.
Carefully remove the cake from the cake ring. Spray rosettes onto the cake with some cream. Coat the edges all around with the rest of the cream. Press the cake crumbs lightly with a pallet. Chill for at least 3 hours.
Decorate as desired with chocolate rolls.
Tip for homemade chocolate rolls: Melt approx. 50 g of chocolate in a hot water bath (for a marble look, melt white chocolate extra). Spread thinly on a marble plate (or another smooth cold plate) with a tablespoon.
Place in the freezer for about 10 minutes. Remove and scrape into chips or rolls with a scraper. Store cool on baking paper in tins, keeps for about 1 week.