1. Bring a large pot of water to a boil; add 1 teaspoon salt. Add green beans and cook until bright green and crisptender, 2 to 4 minutes. Transfer to a bowl of ice and cold water to stop cooking. When cooled, drain and pat dry. (Can be made ahead. Place in a plastic storage bag and chill up to 1 day.) Transfer to a large bowl.
2. Combine mint, almonds, remaining 1/2 teaspoon salt and the zest in a food processor. With motor running, add oil in a stream and blend until pureed, for pesto.
3. Add pesto to green beans and toss until coated well. Transfer to a large serving platter and garnish with mint leaves, if desired.