1 cup dry brown rice, cooked according to package directions and cooled
1 tablespoon chopped fresh parsley
1 tablespoon shopped fresh thyme
Toast the walnut pieces over medium-high heat in a large, dry skillet. Stir often and cook for 3 minutes, or until you begin to smell their nutty aroma. Remove from the heat and transfer the nuts to a bowl to cool.
Add the olive oil to the skillet and return it to medium heat. Add the onions. Cook, stirring often for 1 minute. The onion will begin to turn golden brown in spots as it cooks in the oil. Stir in the mushrooms and thyme and cook for about 2 minutes. They will soften and shrink, but still have a somewhat firm bite. Stir in the walnuts and cook for another 30 seconds.
Remove the skillet from the heat and add the lemon juice, salt, and pepper. Stir well and let cool to room temperature.
Transfer the rice to a large bowl. Add the mushrooms. Toss to mix the ingredients. Sprinkle with parsley before serving at room temperature or chilled.