Cook blueberries with 75 g sugar to a compote, let it cool down and put it in a cool place
Cut the vanilla pods lengthwise and scrape out the pulp. Mix vanilla pulp, eggs, salt and 250 g sugar over a warm water bath with a whisk until the sugar has dissolved. Remove from the water bath and beat with the whisk of the hand mixer until foamy. Whip the cream until stiff and fold into the egg mixture
Pour vanilla cream into a ring cake tin (2.4 litres). Add the blueberry compote and mix in streaks with a long spoon. Freeze for about 2 hours
Put the lady fingers in a freezer bag and crumble them with the rolling pin. Melt the butter in a pot, mix with the crumbs and place on the ring cake. Freeze for another approx. 4 hours
Hold the ring cake pan briefly in hot water and turn it over onto a plate. Serve immediately
waiting time approx. 6 1/2 hours