Haricot Vert and Red-Onion Salad with Pistou

PreparationMake pistou: Purée all pistou ingredients in a food processor until basil is finely chopped. Make salad: Soak onion in cold water 15 minutes, then drain in a colander and pat dry. While onion soaks, cook beans in a 6- to 8-quart pot of boiling salted water, uncovered, stirring occasionally, until just tender, 3 to 6 minutes, then drain in a large colander. Transfer to a large bowl of ice and cold water to stop cooking, then drain again and pat dry. Toss beans and onion with pistou. Season with salt and pepper. Cooks' notes:Pistou can be made 6 hours ahead and transferred to a small bowl, then chilled, covered. Beans can be cooked 1 day ahead and chilled in a sealed large plastic bag lined with paper towels.

PreparationMake pistou: Purée all pistou ingredients in a food processor until basil is finely chopped. Make salad: Soak onion in cold water 15 minutes, then drain in a colander and pat dry. While onion soaks, cook beans in a 6- to 8-quart pot of boiling salted water, uncovered, stirring occasionally, until just tender, 3 to 6 minutes, then drain in a large colander. Transfer to a large bowl of ice and cold water to stop cooking, then drain again and pat dry. Toss beans and onion with pistou. Season with salt and pepper. Cooks' notes:Pistou can be made 6 hours ahead and transferred to a small bowl, then chilled, covered. Beans can be cooked 1 day ahead and chilled in a sealed large plastic bag lined with paper towels.