Place brisket in a large enough pot to hold it and cover with cold water.
Bring to boil; reduce heat and simmer, covered, for one hour. This helps draw out extra salt/
Remove brisket from the pan and place in the crockpot.
Top with garlic, onions, mustard and black pepper, then pour beer over all.
Cover crockpot and cook on the HIGH setting for 6 hours or until internal temp reads 200F.
Remove brisket from crock and rest for 15-20 minutes before slicing across the grain.
You can serve onions with if you like. I did.
For the cabbage, place the wedges in a large sauce pan with a couple inches of water and bring to a boil; then reduce heat, cover and simmer for about 20 minutes or until tender with a fork. I do it on the stove because the cabbage turns out better and everything gets dome at the same time.
I serve my corned beef with grated horseradish and find it delicious.