In a large mixing bowl, whisk the heavy cream until it just starts to thicken. Add the sugar, malt powder, and vanilla and continue whisking until soft to medium peaks form; the cream should be floppy and light. (Note: You can start the whipping process in a stand mixer or with a handheld mixer, but finish whipping the cream by hand to prevent over-beating the cream.)
Place a chocolate wafer on a sheet pan. Drop a rounded teaspoon of whipped cream (I used a small spring-form ice cream scoop) onto the center of the wafer. Use the back of the spoon or your finger to pat the mound of whipped cream into a flattened disk, leaving about 1/8-inch to 1/4-inch space around the edge of the cookie. Gently press another wafer on top of the whipped cream until the frosting is flush with the edges. Continue until you have stacked 6 cookies to make one "mini" cake, finishing off with a coat of whipped cream. (For a more polished look, you can pipe the whipped cream over the tops of the cakes after you have assembled them.)
Repeat the process with the remaining chocolate wafers. If the whipped cream starts to firm up while you are assembling the cakes (you want it to be fairly loose), stir in a tablespoon or two of heavy cream as needed to keep it malleable. The "stiffer" the cream, the less smooth and professional the edges will look.
Transfer the sheet pan to the refrigerator and chill for a minimum of 6 hours, but preferably overnight. Garnish cakes with a cherry, chocolate covered espresso beans, chocolate shavings, chopped pistachios, or leftover ground wafers before serving.