Heat the oven to 350°F/180°C. Spread the nuts on a baking sheet and toast in the oven until slightly darkened and fragrant, about 8 minutes. Remove, chop, and set aside.
Top and tail the green beans, and cook them in a large pot of boiling salted water, until tender. Drain and rinse under cold running water to set the colour.
Heat the oil in a skillet, add the shallot, one minute, then add the beans and toss to heat through. Season with salt and pepper. Add a squirt of lemon juice. Remove from the heat and stir in the crème fraîche to coat. Toss in the hazelnuts and chopped herbs. Arrange on a platter, and serve.