In a small bowl combine milk and the 1/4 cup walnuts; set aside.
In a large skillet cook pork and onion over medium heat until browned, using a wooden spoon to break up pork as it cooks. Drain off fat. Add tomatoes, apple, the diced chile peppers, the 1/2 teaspoon salt, the pumpkin pie spice, and cumin to pork mixture in skillet. Bring to boiling. Stir in rice. Reduce heat. Simmer, uncovered, until most of the liquid evaporates.
For sauce, transfer milk and walnuts to a blender or food processor. Add crema, bread crumbs, cream cheese, brown sugar, and cinnamon. Cover and blend or process until very smooth. Season to taste with additional salt and white pepper.
Spoon about 1/3 cup of the sauce onto each of four serving plates. Spoon one-fourth of the pork mixture into a 6-ounce ramekin. Invert pork mixture onto the sauce on one of the plates; remove ramekin. If using whole green chile peppers, cut each pepper in half lengthwise; wrap chile pepper halves around the edges of pork mixture, as desired. Repeat with the remaining pork mixture and, if desired, the remaining whole green chile peppers. Garnish plates with additional chopped walnuts, parsley, and/or pomegranate seeds.