Line an 8-by-8-inch or 9-by-9-inch baking dish with foil or parchment paper, leaving a 2-inch overhang. Set aside. Put the cookies in a zip-top plastic bag and roughly crush them with a rolling ...

Line the base of a 23cm loose bottom round baking tin with parchment paper. In a food processor, add the 40 Oreo biscuits (and filling) to a food processor and blitz until a fine crumb is reached.