Preheat the oven to 375 degrees F. Spread the hazelnuts on a baking sheet and bake until toasted, about 7 minutes. Let cool slightly, then rub with a kitchen towel to remove the skins; roughly chop and set aside.
Fill a large bowl with ice water and set aside. Bring a large pot of salted water to a boil. Add the haricots verts and cook until crisp-tender, 5 to 7 minutes. Drain and immediately transfer to the ice bath; let sit until cool, about 2 minutes. Drain and pat dry.
Melt the butter in a large skillet over medium heat and cook, stirring occasionally with a rubber spatula, until golden brown flecks appear and the butter smells nutty, about 4 minutes. Add the hazelnuts and cook 30 seconds. Remove the hazelnuts and all but 2 tablespoons of the browned butter to a small bowl; cover to keep warm.
Add the broth to the skillet and season with 1 teaspoon salt. Bring to a boil over high heat, then add half of the haricots verts and cook until warmed through, about 2 minutes. Transfer to a platter using tongs. Repeat with the remaining haricots verts. Top with the hazelnuts. Season with salt and sprinkle with the lemon zest.
Photograph by Chris Court
Courtesy of Food Network Magazine