Cook 1 1/2 pounds green beans in salted boiling water until crisp-tender, 2 minutes. Drain and transfer to a bowl of ice water to cool, then drain and pat dry. Whisk 2 tablespoons each sherry vinegar and orange juice, 2 teaspoons dijon mustard and 1/2 teaspoon kosher salt in a large bowl; whisk in 1/4 cup olive oil. Add 1 thinly sliced shallot and let sit 10 minutes. Add the green beans, 2 heads torn frisée, the segments of 2 oranges and 1/3 cup chopped toasted pistachios; season with salt and pepper and toss.