- 1/2 pound haricots verts, trimmed
- 3 hard-boiled large eggs, quartered
- 2 tablespoons mayonnaise
- 1/2 teaspoon grated lemon zest
- 1/2 tablespoon fresh lemon juice, or to taste
- 1/3 cup minced scallions (2 to 3)
- 15 thin slices prosciutto (about 7 by 3 inches; 1/2 pound)
- Cook haricots verts in a large pot of boiling salted water (3 tablespoons salt for 6 quarts water), uncovered, until just tender, 4 to 5 minutes. Drain, then transfer to an ice bath to stop cooking. Drain and pat dry.
- Force hard-boiled eggs through a medium-mesh sieve into a bowl using a rubber spatula. Stir in mayonnaise, zest, lemon juice, scallions, 1/2 teaspoon pepper, and 1/4 teaspoon salt (or to taste).
- Place a sushi mat with slats running crosswise or a 9-inch square of parchment paper on a work surface. Arrange 3 slices prosciutto perpendicular to slats and slightly overlapping to form a 9- by 7-inch rectangle.
- Spread about 1 tablespoon egg mixture evenly across bottom half of prosciutto rectangle. Arrange beans on egg side by side and end to end, overlapping ends, in 8 tight rows parallel to slats. Spread another tablespoon egg mixture over beans.
- Roll up prosciutto and beans tightly with aid of mat. Transfer roll, seam side down, to a cutting board, then trim ends and cut crosswise into about 10 (3/4-inch) pieces. Make and cut 4 more rolls. Turn pieces upright to serve.