chopped, (reserve 4 halves for garnish)
Preheat oven to 350℉ (180℃).
Spread walnuts evenly on a cookie sheet; bake 10 to 12 minutes until fragrant and lightly toasted.
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.