Bring a large pot of lightly-salted water to a boil. Add haricots verts and cook until crisp-tender, about 5-7 minutes. Immediately transfer green beans to a bowl of ice water to stop the cooking process, drain, and set aside.
Melt butter over medium heat in a skillet. When butter is melted and starts foaming, continue cooking, swirling the pan frequently, until butter fats start turning a light golden brown and are fragrant.
Turn off the heat and stir in lemon juice, herbs, 1/2 teaspoon kosher salt, and 1/2 teaspoon freshly ground black pepper.
Add green beans to the pan and toss to coat with the brown butter mixture. Return pan to medium heat, and sauté just until haricots verts are heated through, about 3 minutes.
Season to taste with additional salt and pepper. Serve immediately.