Melt roughly 2 tbsp of the butter. Add onion to sauté until semi-clear. Add garlic and sauté for about 30 seconds more. Add ground beef, 1 tsp of pepper, salt and mustard. Cook until the meat has browned. Add cooked rice and carrots mix. Remove from heat and set aside.
Remove the core of the cabbage and place in boiling water. Boil for about 5 minutes. Peel softened leaves and set aside. If inner leaves are still tough, return to the boiling water until soften. Repeat until all leaves are removed.
Melt remaining butter in sauce pan and add tomato sauce and remaining 1 tsp pepper. Allow sauce to simmer while you assemble cabbage rolls.
Spoon filling onto the end of a leaf and roll, tucking in sides as you go. Repeat until all leaves are used. Please rolls into a greased casserole dish and spoon sauce over rolls.
Place in oven for 30 minutes at 325 degrees.
We love to serve the rolls with mashed potatoes. It's a hearty meal! To lighten it up, feel free to serve with salad or as a stand alone dish!