Combine mint, garlic, almonds (and rosemary leaves, if using), lemon zest and lemon juice in the bowl of a food processor and chop.
Leaving the motor running, add olive oil in a slow, steady stream until mixture is moist (but not too oily).
Add cheese, salt and pepper. Pulse until just mixed
Process briefly to combine, then scrape into a bowl and cover until ready to use. Can be made a few hours in advance.
Remove the ends of the green beans and place in a steamer basket set over an inch of water and cover.
Place over high heat. Let cook for 8 to 10 minutes. Green beans are done when bright green and just tender. Be careful not to overcook them.
Transfer green beans to a bowl and toss with 2 to 3 tablespoons of mint pesto. Serve immediately or at room temperature.
Notes
* You’ll have leftover pesto which you can save for some more green beans or serve with something else like lamb, shrimp or potatoes. * This pesto freezes well so you can enjoy some summer flavors in the middle of winter.