Place one of the oven racks in the lower third of the oven and preheat the oven to 350°F. Lightly grease a 9×13-inch casserole dish with nonstick spray. Set aside.
Combine the rice and water in a medium saucepan and bring to a boil over high. Reduce the heat and simmer uncovered on low, stirring occasionally, for 25 minutes, until the rice is partially cooked (it will keep baking in the oven). Strain the rice through a fine mesh strainer and rinse with cold water to remove any excess liquid and starch. Place in a large bowl and set aside. Keep the pot handy (no need to clean it).
Meanwhile, core the cabbage: Peel off any dirty leaves from the cabbage head. Sit the cabbage on your cutting board so the stem side is facing directly upwards. Using a paring knife, make 4 cuts that are each 1/2-inch away from the core so that the cuts form a square. Make each cut at an angle so that your knife is pointing down towards the core as you slice. Shimmy the knife through each corner of the square shape to help loosen the core. Then, pull on the cabbage stem area to remove the core. You may need to wiggle your paring knife around the square again to help loosen it. Discard the core.
Simmer the cabbage: Fill a large pot with 2 inches of water. Bring to a boil, then reduce the heat to a medium-low heat such that the water simmers. Carefully lower the cabbage (with its core side facing the bottom of the pot and the top of the head facing up) into the pot and cover it. Let simmer for 15 minutes. With a slotted spoon or handheld medium sieve, carefully lift the cabbage out of the water. Let cool until you can handle it safely, 10-15 minutes.
To the now-empty pot you used to cook the rice, add 2 tablespoons of oil and the onion. Sauté over medium-low heat for 10 minutes until softened. Add the garlic and saute until fragrant, about 1 minute.
Add the onion-garlic mixture to the bowl of rice.
Add the ground beef, egg, 1 teaspoon oregano, 1/2 teaspoon nutmeg, 1/4 teaspoon pepper, 1 teaspoon salt, and 2 tablespoons chopped parsley. With a fork or your hands, mix to combine, making sure not to overwork the meat. Only mix until just combined. Set aside.
Place the semi-cooled, cooked cabbage on a cutting board. Peel 12 larger in-tact leaves off of the cabbage (peel from the core side for easy removal). Trim any tough, thick ribs from the stem side of the cabbage leaf by using a paring knife to cut a V shape around the rib to remove it. (Don’t cut off too much or it will be hard to roll.) Set aside.
Quarter and chop any remaining cabbage into thin 1/4-inch strips. Scatter evenly over the bottom of the baking dish.
Assemble the rolls: Add 2 heaping tablespoons of the beef mixture to the center of a cabbage leaf (it’s OK if the leaf is still a little damp).
Fold the sides of the leaf inwards to cover the meat, then begin rolling from the stem side, until you have a cabbage roll.
Place seam side down, in the prepared baking dish. Repeat with remaining cabbage until you have 12 rolls. If there is any leftover beef mixture, roll it into small (about 1-to 1 1/2-inch) meatballs and arrange them in the pan in between the rolls.
To the now-empty bowl that held the beef mixture, add the tomato sauce. Add 1/2 cup water to one of the empty tomato sauce cans, swish around, and add the water to the bowl. Mix in the crushed tomatoes, garlic powder, bay leaf, vinegar, honey, and remaining 1/2 teaspoon dried oregano, 1/2 teaspoon nutmeg, 1/4 teaspoon pepper, 1 teaspoon salt, 2 tablespoons chopped parsley. Stir gently to combine.
Carefully pour the sauce over the cabbage rolls. Lift the cabbage rolls a bit to ensure the sauce gets distributed beneath them.
Spray a piece of foil large enough to cover the pan with nonstick spray. Cover the pan tightly with the foil, placing it spray-side down. Place onto a rimmed baking sheet to catch any drips. Bake until the cabbage is nearly fork tender and easily cuts with a paring knife, about 1 1/2 hours.
Remove from the oven and carefully uncover the pan. Use a spoon to ladle the hot sauce from the bottom of the pan over each cabbage roll. Recover the pan securely with foil and allow to rest at room temperature for 30 minutes.
Remove and discard the bay leaves. Serve right away or store in the fridge for up to 4 days.
