Brain-boosting whole grains and lean grilled chicken get brightness from a tangy vinaigrette, sweetness from blueberries, and a nice crunch from walnuts. Sub in farro, quinoa, or any other whole grain for the wheat berries.
Bring a large pot of water to a boil. Add wheat berries, reduce heat to medium, and simmer until just tender, 45 to 50 minutes. Add green beans, and simmer 3 minutes. Drain wheat berries and green beans; rinse under cold water until cool. Transfer to a bowl.
Coat a cast-iron grill pan or skillet with cooking spray, and heat over medium-high. Sprinkle chicken with ½ teaspoon of the salt and ¼ teaspoon of the pepper. Add chicken to pan, and grill until a thermometer registers 160°F, about 5 minutes per side. Transfer chicken to a cutting board, and let rest 5 minutes before slicing.
Meanwhile, whisk together oil, vinegar, tarragon, mustard, and remaining ¾ teaspoon salt and ¼ teaspoon pepper.
Add blueberries, walnuts, and vinaigrette to wheat berry mixture in bowl; toss to combine and coat. Divide mixture evenly among 4 shallow bowls. Slice chicken against the grain, then divide chicken among bowls.