Bring a medium pot of cold water to a boil over high heat and salt it generously. Trim the stem end off the green beans. Peel and finely chop the shallot.

Drop the green beans into the boiling water and cook, uncovered, until crisp tender, about 4 minutes. Drain in a colander set in the sink and rinse with very cold water until cool. Drain well and pat dry with paper towels. (The vegetables can be prepared up to this point, up to 4 hours ahead.)

Heat the olive oil in a large skillet over medium heat. Add the shallot and cook, stirring occasionally, until the shallot is just golden, about 2 minutes. Add the green beans, increase the heat to high, and cook, stirring occasionally, until the beans are heated through, about 4 minutes. Season with the 1/2 teaspoon salt and some pepper and serve immediately.