Roast the nuts in a pan without fat, then chop roughly. Put the biscuits in a freezer bag and crumble with the cake roll. Melt 150 g butter in a saucepan and mix with the cookie crumbs. Brush the bottom of an angular springform pan (20 x 20 cm) thinly with oil. Put the biscuit mixture into the tin, press it firmly and put it in a cool place.
Roughly chop the chocolate. Heat cream and 25 g butter in a saucepan (do not bring to the boil). Melt chocolate in it. Stir nuts into the chocolate and spread on the speculoos base. Chill the cake for 1 1/2 hours, then cut into small cubes with a hot knife
1 1/2 hours waiting time