Chop 150 g chocolate and melt over a warm water bath. Finely crumble the biscuits in a freezer bag with a dough roll. Melt butter. Mix cookie crumbs, chocolate, butter and 2 tablespoons of cocoa.
Pour the crumb mixture into a springform pan (26 cm Ø) that has been greased with oil. Press down firmly to form a base and a rim about 4 cm high. Chill for 30 minutes.
Chop 50 g chocolate, melt 25 g over a warm water bath. Puree 25 g chopped chocolate with dates, oil and 1 tablespoon of cocoa. Stir the liquid chocolate into the puree. Chill the mixture for about 30 minutes.
Heat milk in a saucepan, add 375 g marshmallows and dissolve over medium heat while stirring. Stir in lemon juice, remove from heat and allow to cool for about 30 minutes.
Form approx. 15 balls from the date mass and put them back in the fridge. Whip the cream with the whisk of the hand mixer until stiff. Fold the cream into the marshmallow mixture. Spread the marshmallow cream on the base, spread date balls on the cream and press in a little.
Keep it cold overnight.
Cut 10 g marshmallows into small pieces. Carefully remove the cake from the tin, place on a plate and decorate with marshmallows.