1. Preheat oven to 400°.
2. Place squash halves, cut sides down, on a foil-lined baking sheet coated with cooking spray. Bake at 400° for 30 minutes or until tender. Cool. Scoop out pulp; discard peel. Mash pulp. Combine oregano, squash pulp, and butter in a large bowl. Stir in 2 ounces (about 1/2 cup) cheese, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Working with 1 wonton wrapper at a time (cover remaining wrappers with a damp towel to keep them from drying), spoon about 1 1/2 teaspoons squash mixture into center of each wrapper. Moisten edges of wrapper with beaten egg; bring 2 opposite corners together. Pinch edges together to seal, forming a triangle. Repeat procedure with remaining wrappers, squash mixture, and egg. Cover ravioli loosely with a towel to prevent drying.
3. Place garlic in a food processor, and pulse until finely chopped. Add remaining 1/2 ounce (about 2 tablespoons) cheese, remaining 1/8 teaspoon salt, remaining 1/4 teaspoon pepper, spinach, basil, and 2 tablespoons walnuts. With processor on, slowly pour oil, broth, and juice through food chute. Process until well blended. Place pesto in a large bowl.
4. Bring 6 quarts water to a boil in a large Dutch oven. Add half of ravioli; cook 3 minutes or until thoroughly cooked. Remove ravioli with a slotted spoon. Repeat procedure with remaining ravioli. Add ravioli to pesto; toss gently to coat. Arrange 6 ravioli on each of 6 plates; sprinkle each serving with 1 teaspoon walnuts.