Heat the olive oil in a large skillet over medium heat. Add the shallots and cook, stirring, until softened, about 1 minute. Add the green beans and salt and pepper to taste. Saute, stirring occasionally, until crisp tender, about 5 minutes. Transfer to a serving dish and set aside.
Return the skillet to medium-high heat and add the cream, thyme, lemon juice and zest, and chicken broth. Bring to a simmer and let reduce by half, until thick enough to coat the back of a spoon, about 5 minutes. Remove from the heat and stir in the sour cream. Add salt and pepper to taste.
Pour the dressing over the green beans to serve.