1/4 cup coarsely chopped walnuts
1 pound green beans
1 teaspoon salt plus more to taste
Freshly ground black pepper
1 1/2 tablespoon freshly squeezed lemon juice (about 1/2 lemon)
3 tablespoons extra virgin olive oil
4 ounces Parmesan cheese, thinly shaved (about 1/2 cup)
Toast the walnuts in a dry, heavy skillet (preferably cast iron)
over high heat until they start to brown in spots and become fragrant. (Be careful not to overtoast them, as they will burn very quickly once toasted.) Immediately transfer the nuts to a dish to cool.
Bring a large pot of water to a boil. Add the beans and salt; cook until tender but still firm, 3 to 5 minutes. Transfer the beans to a colander in the sink and run cold water over them. Trim the beans if necessary.
Toss the beans and walnuts in a large bowl and season with salt and pepper to taste.
In a small bowl, whisk the lemon juice and olive oil until well combined. Pour this mixture over the beans and toss until well coated. Transfer the salad to a serving platter or to individual plates. Scatter the Parmesan shavings on top.