Cook vegetable mixture: Preheat oven to 375°F. Heat oil in a Dutch oven over medium-high. Add onion, bell pepper, and celery; cook, stirring occasionally, until vegetables are tender, about 5 minutes. Add garlic; cook, stirring constantly, until fragrant, about 30 seconds. Stir in stock, tomato paste, tomatoes, and 2 teaspoons of the Creole seasoning; bring to a boil over medium-high. Reduce to a simmer over medium-low, and cook, uncovered and stirring occasionally, until sauce is thickened slightly and flavors have melded, 12 to 15 minutes. Remove sauce from heat, and set aside.

Cook cabbage: Place cabbage in another large pot, cored side up, and fill with water to cover cabbage by 2 to 3 inches; bring to a boil over high. Reduce heat to medium to maintain a simmer, and cook until cabbage leaves are softened, about 5 minutes.

Prepare cabbage leaves: Using tongs, transfer cabbage to a cutting board. Remove the 10 largest leaves; place on paper towels, and pat dry, reserving remaining leaves for another use. Cut out and discard ribs of leaves, leaving a “V” shape slit. Set cabbage leaves aside.

Make cabbage roll filling: Place sausage, beef, egg, rice, ½ cup of the tomato sauce, and remaining 1 teaspoon Creole seasoning in a medium bowl; mix gently with clean hands or a fork until incorporated.

Fill and roll the leaves: Evenly portion out filling into centers of cabbage leaves (about a heaping ¼ cup per leaf). Shape each filling into a log (about 3 inches long and 1 inch wide). Starting at the base of each leaf where you cut the “V”, fold end of leaf over filling, then fold in sides. Roll each leaf like a burrito into a tight cylinder.

Add rolls to baking dish: Place cabbage rolls in 2 side-by-side rows (5 rolls in each row) in a 13- x 9-inch baking dish.

Add tomato sauce, and bake: Top cabbage rolls evenly with remaining 3 ½ cups tomato sauce. Cover tightly with aluminum foil. Bake in preheated oven until cabbage can be cut with a spoon, about 1 hour, 30 minutes. Let cool 15 minutes. Garnish with parsley before serving.