Norwegian Cabbage Rolls

Name: Norwegian Cabbage Rolls
Ingredients: 2 tablespoons unsalted butter; 1 large yellow onion, finely chopped; 1 pound 80% lean ground beef; 1 cup cooked rice; 0.5 cup heavy whipping cream; 1 large egg; 1 tablespoon finely chopped fresh Italian parsley; 2 teaspoons potato starch; 2 teaspoons salt; 1 teaspoon coarsely ground black pepper; 1 teaspoon whole caraway seeds; 0.25 teaspoon ground ginger; 0.25 teaspoon ground nutmeg; 0.125 teaspoon ground cloves; 2 large heads cabbage, cored