Heat a large nonstick skillet over medium-high heat for 1 minute. Add mushrooms and onion; cook, stirring often for about 10 minutes, until mushroom liquid has evaporated and onion is golden brown. Add rice, broth, vinegar, bitters, rosemary and pepper; bring to a boil. Reduce heat, cover and simmer 40 minutes until rice is tender and liquid is absorbed. Add reserved walnuts; toss to combine. Sprinkle with parsley, garnish with walnut halves and serve. Each serving (1 cup) provides: 1 FA, 2-1/4 V, 1/2 P, 1 B, 10 C. Per serving: 231 cal, 6 g pro, 30 g car, 10 g fat: 6 g poly, 2 g mono, 1 g sat 10 g sod, 0 mg chol