For the Cod, mix miso, mirin, oil, sake, sugar, Spice Blend and soy sauce in small bowl until well blended. Place fish in large resealable plastic bag or glass dish. Add marinade; turn to coat well. Refrigerate 1 hour.
Meanwhile, for the Miso Butter, mix all ingredients in small bowl until well blended. Set aside.
For the Butternut Squash, place butternut squash and water in medium saucepan. Bring to boil. Reduce heat to low; cover and simmer 15 to 20 minutes or until tender. Drain well. Place butternut squash, Miso Butter, orange peel and sea salt in food processor; cover. Process until smooth. Or mash with potato masher until smooth. Keep warm.
Remove cod from marinade and place on broiler pan. Discard any remaining marinade. Broil 2 to 3 inches from heat for 12 minutes or until fish flakes easily with a fork. Do not turn fish.
For the Bok Choy, melt Miso Butter with garlic powder and sea salt in large skillet on medium heat. Add bok choy and bell pepper; stir-fry 2 to 3 minutes or until tender-crisp. To serve, divide squash puree and stir-fried vegetables among each of 6 plates. Top each with a cod fillet. Sprinkle with additional Spice Blend, if desired.