For the squash filling: Preheat the oven to 350 degrees F. Roast the squash, about 1 hour 15 minutes, and then deseed and scoop out the flesh. Puree the flesh in a food processor.
Preheat the broiler. Roast the poblano peppers until charred on the outside, and then peel, deseed and chop.
Saute the collards with the onions and vinegar, sprinkle with salt and white pepper, and cook until tender. Drain, and then mix with the squash, poblano peppers, cream cheese and nutmeg.
For the pasta: Combine the flour, whole-wheat flour, salt, egg yolks and whole eggs in a food processor or by hand until a dough forms. Knead the dough until it's smooth and elastic, about 10 minutes, and then wrap in plastic and refrigerate for at least 30 minutes.
For the fontina veloute sauce: Melt the butter in a saucepan over medium heat. Add the onions and saute until soft. Stir in the flour and make a light roux by slowly adding the stock, and then slowly adding the cream, stirring constantly. Lower the temperature and add the fontina and Parmesan a little at a time, stirring continuously. Sprinkle with salt and white pepper.
For assembling: Bring a large pot of salted water to a boil. Roll out the pasta dough to desired thickness using a rolling pin or pasta machine. Stuff the dough with the squash filling using a large ravioli mold, wetting the seams before sealing. Poach the ravioli in the boiling water until they float, 3 to 5 minutes.
Serve the ravioli topped with the fontina veloute sauce and garnish with chopped chives.
This recipe was provided by a chef, restaurant or culinary professional and may have been scaled down from a bulk recipe. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.