Bring a pot of salted water to a boil. Add the cabbage leaves and blanch for 2 to 3 minutes until softened. Drain and set aside.
12 - 14 large cabbage leaves
In a large bowl, mix together the filling ingredients until well combined. This is done easiest with your hands.
1 pound ground beef, ½ pound ground pork sausage, ½ cup onion, ½ cup bell pepper, 1 egg, ¼ cup milk, 1 cup rice, 2 Tablespoons Worcestershire sauce, 2 teaspoons kosher salt
In a separate bowl, whisk together the sauce ingredients.
1 (15 ounce) can, 2 Tablespoons brown sugar, 1 Tablespoon apple cider vinegar, 1 Tablespoon fresh parsley, 1 teaspoon kosher salt, 1 teaspoon black pepper
To assemble, lay out each cabbage leaf, spoon about ¼ cup of filling along one edge. Roll up each leaf, tucking the sides in as you go to completely enclose the filling.
Coat the inside of a slow cooker with the nonstick spray, then arrange the rolls along the bottom, seam side down. It may be necessary to stack a few on top of each other.
Nonstick cooking spray
Pour the sauce over the rolls, spreading it out as evenly as possible.
Cover and cook on high for 4 to 5 hours, or on low for 7 to 8 hours.