step 1Boil the potatoes in rapidly boiling salted water until they are tender - 15 to 20 minutes. Drain them and set them aside to cool slightly. Slice them thin.
step 2Cut the focaccia into 8 pieces of equal size.
step 3Combine, the tuna, garlic, and mayonnaise in a food processor, and pulse until the mixture is very smooth.
step 4Spread the tuna mayonnaise over the top of each piece of focaccia.
step 5For each sandwich, cover one piece of the focaccia with potato slices and the other piece with egg slices.
step 6Season both pieces with salt and pepper.
step 7Add greens, or cabbage, close to the sandwich, and cut in half.