Preheat oven to 375 degrees. Spray a foil-lined baking sheet lightly with nonstick spray, and place sweet potato halves, cut side down, on prepared sheet. Prick skin side a few times with a fork. Bake until soft, about 25-35 minutes. Once cool enough to handle, scoop the sweet potato from the skin and mash the filling with a fork.

Heat oil in a large skillet over medium heat, add 1/2 tsp salt and onion, then saute for 3 minutes, or until onions just soften and turn light golden. Turn off heat and stir in mashed sweet potato, ricotta cheese, 4 ounces of Gorgonzola cheese, black pepper and nutmeg. Mix well and set aside.

To make ravioli, a dampen a clean dishtowel to cover and keep the wonton wrappers from drying out. Lay about 4 wrappers on a clean dry surface and place about 1/2 tablespoon of filling in the center of each. Lightly dampen the edges of wrappers with cool water, and fold one side over the filling to make a half-circle, pressing the edges to seal. Repeat with remaining wrappers. Bring a 4-5 quart stock pot of water to a boil, add 1/2 tsp salt, then carefully immerse ravioli and radicchio. Reduce heat and simmer for 5-7 minutes. Drain and set aside.

Melt butter in a 12-inch skillet over medium-low heat, add remaining salt, sage, parsley and walnuts. Saute for 1 minute, then add ravioli and radicchio, stirring gently. Remove and serve topped with remaining parsley, the chives, and remaining Gorgonzola cheese.