Preheat oven to 350 degrees. Toast sesame buns, 4–5 minutes. On both halves of the buns, spread bacon mayonnaise.
Cook sausage patties in skillet over medium-high heat until cooked through. Top patties with 1 slice each of American cheese, and place 1 patty each on the bottom half of buns. Top patties with 1 egg each.
In a bowl, dress watercress with olive oil, salt, and pepper and mix thoroughly. Top eggs with evenly divided watercress. Place top buns on each sandwich. Be careful not to break yolks until eating.