Make hard boiled eggs. (TIP: I always boil 1 dozen when I bring mine home from the neighbor so I can have an easy snack in the fridge. My kids love Deviled Eggs!) Cook green beans in a large pot of boiling salted water (1 TBS salt per 2 quarts water), uncovered, until just tender, about 4 minutes. Drain and place into a ice cold water bath to stop cooking. Drain and pat dry.
Place the hard boiled eggs, mayonnaise, zest, lemon juice, scallions, 1/2 tsp pepper, and 1/4 tsp sea salt into a food processor and blend until smooth.
Place 3 slices prosciutto perpendicular to slats and slightly overlapping to form a large 9- by 7-inch rectangle on a sushi mat with slats running crosswise or a 9-inch square of parchment paper on a work surface.
Spread some of the egg mixture evenly across bottom half of prosciutto rectangle. Place the beans on egg side by side and end to end, overlapping ends, in 8 tight rows parallel to slats. Spread another tablespoon of the eggs over beans.
Roll up the sushi very tight using the mat. Transfer the roll, seam side down, to a cutting board. Trim the ends and cut crosswise into about 10 (3/4-inch) pieces. Repeat and cut 4 rolls. Turn pieces upright to serve. This recipe was inspired by Gourmet Magazine.