Rinse the rice in cold water until the water runs clear—this removes excess starch and prevents the final dish from becoming gummy. While the rice drains, dice the onion into 1/2-inch pieces, chop the red pepper into similar-sized pieces, mince the garlic, chop the cabbage into 1-inch squares, and shred the mozzarella cheese from a block (block cheese melts more smoothly than pre-shredded). Measure out all remaining ingredients and have them ready before you start cooking.
Heat a large skillet over medium-high heat and add the ground beef, breaking it apart as it cooks. Once the beef is mostly browned (about 3-4 minutes), add the diced onion and red pepper, stirring occasionally until the vegetables soften and the beef is fully cooked, about 2 more minutes. I like using an 85/15 ground beef ratio because it has enough fat to keep everything moist without leaving excess grease to drain. Carefully pour off excess fat if needed, leaving about 1 tablespoon in the pan for flavor.
Add the minced garlic to the skillet and cook for 30 seconds until fragrant, then immediately stir in the tomato paste, Italian seasoning, smoked paprika, and salt. Cook this mixture for 1 minute, stirring constantly—this blooming technique deepens the flavors and prevents the garlic from burning. The tomato paste will caramelize slightly on the bottom of the pan, which adds complexity to the final dish.
Add the diced tomatoes, rinsed rice, beef stock, chopped cabbage, soy sauce, Worcestershire sauce, and red pepper flakes, stirring well to combine and prevent the rice from sticking to the bottom. Bring the mixture to a boil over medium-high heat, then reduce to low heat, cover with a lid, and simmer for 20 minutes without lifting the lid. The rice will absorb the liquid and cook perfectly, while the cabbage becomes tender and infuses the dish with flavor. I like to let it sit undisturbed because checking it releases steam and can make the rice cook unevenly.
Remove the skillet from heat and scatter the shredded mozzarella evenly over the top of the rice mixture. Cover the skillet with the lid and let it sit for 2-3 minutes until the cheese is completely melted. Taste the dish and adjust seasoning with additional salt and black pepper as needed, then top with fresh parsley before serving.