Begin by brewing some strong coffee. Let it cool. The coffee mjst be cold before it can be used.
Start by whipping the egg yolks and sugar in the bowl of a stand mixer on high speed until very pale and risen in volume and the whisk leaves a trail
Using the beater attachment, add the mascarpone cream, biscoff spread and vanilla extract. Beat on medium speed until just combined
Switch back to the whisk attachment. Add the double cream and whip on medium high speed until stiff peaks form.
When ready to layer up, dip each biscuit in the coffee, very briefly and create a layer of biscuits 2-deep.
Top with half of the mascarpone cream mixture and level out with a palette knife
Repeat with another 2-deep layer of biscuits and finish off with the remainder of the mascarpone cream.
Cover and chill - ideally overnight, for a minimum of 4 hours