Add enough hot water to a large pot to come two-thirds up the sides and to a boil over high heat. Add the cabbage and return to a boil, using a wooden spoon and a pair of tongs to gently pry away the loose outer leaves as they begin to release from the cabbage. As the leaves become soft and pliable, transfer them to a large baking sheet to drain and cool. Continue working to gently release the outer leaves from the head of cabbage, removing them from the pot as they become soft and pliable. You will need 15 beautiful large leaves and a handful of smaller leaves for lining the pot (torn smaller leaves are ok). Drain and allow the leaves to cool completely. Using a very sharp paring knife, trim away the thick portion of the hard outer vein from the leaves so that they are of even thickness and easily roll-able.

Heat the butter in a medium skillet over medium high heat. Add the onion, celery, and bell pepper and cook until softened, 4 to 6 minutes. Add the garlic, ¼ teaspoon of the salt and the ¼ teaspoon black pepper and cook until fragrant, 1 to 2 minutes longer. Set aside to cool.

In a large bowl, combine the chorizo, rice, egg, 2 tablespoons parsley and the cooled vegetable mixture. Mix gently but thoroughly to combine. Using a measuring cup or portion scoop, spoon ¼ packed cup of the filling onto the center of a cabbage leaf and fold the stem edge of the leaf up and over the filling, then fold over both sides, and lastly, roll the leaf upwards to create a tight little cabbage package. Repeat with the remaining leaves until you have used all of the filling.

Line the bottom of a heavy, grill-proof Dutch oven with a few of the extra wilted cabbage leaves. Position the rolls in the bottom of the pot in a tight even layer. Place any remaining leaves on top of the rolls.

Set aside while you make the sauce; preheat an oven or covered grill to 350 degrees F.

In a medium bowl, whisk together the tomato sauce, tomato paste, beef stock, sugar, crushed red pepper, and the remaining ¾ teaspoon salt. Stir in the bay leaves and pour the sauce over the rolls. 

Cover the Dutch oven and transfer it to the grill over indirect heat. Close the grill and cook the cabbage rolls for 1 ½ hours, or until a fork inserted into the cabbage rolls meets with little resistance. Allow the rolls to sit briefly before serving.

Serve the rolls with some of the sauce spooned over the top; garnish with a dollop of sour cream and a sprinkling of chopped parsley.