1. Preheat oven to 375 degrees F. Line a baking sheet with parchment paper.
2. In a medium saucepan, combine water and wine and bring to a boil over high heat.Add lentils and cook, uncovered, until lentils are tender and liquid is absorbed,about 10 minutes. Remove from heat and set aside.
3. While lentils cook, heat oil in a large nonstick skillet over medium-high heat. Add onion and saute until softened, about 5 minutes. Add chopped portabella stems and baby bella or white mushrooms, garlic, and salt. Saute until mushrooms begin to give off their juices, about 5 minutes, then stir in tomato paste. Continue sauteing until most of the liquid has evaporated. Add mixture to the cooked lentils and stir to combine.
4. Add parsley, basil, olives, and chopped walnuts and mix well.
5. Spray both sides of the portabella caps with olive oil cooking spray. Place caps topside down on the baking sheet. Fill each mushroom with an equal portion of the lentil filling. Place a walnut half in the center of each, then spray tops with cooking spray. Bake until mushrooms are cooked through and soft, about 25 to 30 minutes. If desired, garnish each with a parsley sprig. Serve hot.
Source: Hannaford fresh Magazine, March - April 2013