Bring a large pot of water to a boil; add 1 teaspoon salt. Add green beans and cook until bright green and crisp tender, 2 to 4 minutes. Transfer to a bowl of ice and cold water to stop cooking. When cooled, drain and pat dry. Transfer to a large bowl.
Combine mint, almonds, remaining 1/2 teaspoon of salt and the zest in a food processor. With motor running add olive oil in a stream and blend until pureed for pesto.
Add pesto to green beans and toss until coated well. Transfer to large serving platter and garnish with mint leaves, if desired.