Make the garlic butter. Mash the softened butter with the grated garlic and black pepper in a small bowl until smooth. Don't skip the grating — chopped garlic burns in the Crispi; finely grated dissolves into the butter and toasts evenly.
Build the sandwich. Spread the garlic butter generously on one side of each slice of bread (the outside). Turn slices over. On the inside of one slice, spread a very thin, even layer of Marmite — you should barely see it. Pile all three grated cheeses on top. Close the sandwich, buttered sides facing out.
Load the Crispi. Insert the crisper plate into the small container. Centre the toastie on the plate. Sprinkle the oregano on top if using.
First cook. Attach the PowerPod, press MODE until AIR FRY is lit, and set the timer to 11 minutes. Press START.
Flip at 5 minutes remaining. Lift the PowerPod off, flip the toastie with silicone tongs (the underside should be deep gold), and put it back to finish.
Rest, then slice. Lift onto a board, rest 60 seconds, slice diagonally, eat immediately.