Remove the corned beef from the package. Rinse with cold water and pat dry with paper towels.

Place the corned beef brisket (fat side up), carrots and potatoes in a slow cooker. Add 3 cups of water to the slow cooker, plus the seasoning packet that comes in the corned beef package.

Cover and cook on LOW for 6 hours.

Add the cabbage on top of the corned beef and cook on LOW for another 2 hours.

Remove the cabbage, corned beef, potatoes and carrots from the slow cooker. Slice the corned beef against the grain.

Place the butter, garlic, parsley and salt and pepper in a small bowl. Microwave in 30 second increments or until melted.

Drizzle the garlic butter over the carrots, potatoes and cabbage. Place the meat, potatoes and vegetables on a platter and serve with mustard on the side if desired.