Make Ahead: The green beans, vinaigrette, and pecans can be prepared 1 day ahead.
2. Position a rack in the center of the oven and preheat to 350°F. Spread the pecans on a baking sheet. Bake, stirring occasionally, until toasted and fragrant, about 10 minutes. Cool completely. Coarsely chop 1/4 cup of the pecans and set aside.
3. Combine the remaining 1/2 cup pecans and the balsamic and wine vinegars in a blender. With the machine running, gradually add the oil to make a smooth vinaigrette. Season with salt and pepper. (The vinaigrette and chopped pecans can be prepared up to 1 day ahead, covered and refrigerated.)
4. Toss the green beans with the vinaigrette in a large bowl. Transfer to a serving platter or bowl and sprinkle with the chopped pecans. Serve chilled or at room temperature.
Sandor Katz lives to ferment; it’s his life’s work. The author of The Art of Fermentation shares how to make kombucha at home.