Grind the speculoos until they are very finely crumbly. Mix the yoghurt and mascarpone and add the speculoos powder, mix well.
Beat the cream with icing sugar and cream stiffener. Carefully fold the cream into the speculoos mixture.
Serve either in small dessert bowls or in a large glass bowl. I used dessert bowls and decorated the cream with cinnamon powder and chocolate decorations.