Roughly chop both couvertures and let them melt together with the coconut oil and milk or cream over low heat. If necessary, let the mass cool down a little until it is ready for spraying.
Lay out 1/3 of the biscuits, preferably on a baking sheet lined with baking paper, and pour the chocolate cream onto the biscuit using a piping bag so that the biscuit is well covered. Then put the wooden skewer on top of the chocolate cream and place another biscuit on top. Lay a 3rd layer with the cream and biscuits.
Chill in the refrigerator for at least 5 hours, but preferably overnight, then the cream will set.