Melt the butter and let it cool down a little. Finely crumble the biscuits. Lightly coat a springform pan (26 cm Ø) at the bottom with oil. Mix the crumbs with the butter. Season with 1/4 tsp salt. Pour into the tin and press to a flat bottom. Chill for about 30 minutes.
Soak gelatine in cold water. Mix cream cheese and sugar well with a whisk. Stir in yoghurt and lemon juice. Whip the whipped cream until stiff. Squeeze gelatine well, dissolve. Stir a little cream into the gelatine. Then stir into the remaining cream. Stir in the cream. Quickly fold 150 g blueberries into the cream. Spread the cream on the base and smooth it down. Chill for at least 4 hours.
Remove the cake from the mould. Warm the jam slightly, fold in the remaining blueberries and spread on the cake. Keep cold until serving.