Gather your ingredients so that you have everything close at hand on the counter or table. Remove corned beef from package and set in slow cooker.
Sprinkle the meat with enclosed seasoning packet. Pour beef stock and dark beer over the meat.
Cook on high for 6 hours.
Using a cutting board and Santoku knife, slice head of cabbage into wedges. Halve the onion and slice.
Place cabbage and onion over the corned beef and season with kosher salt and freshly ground black pepper. Press down into the juices with a spoon.
Cook another 2 hours on high until cabbage is tender and meat is tender and falls apart.
(If desired, add sliced carrots and red potatoes at the same time as the cabbage. If needed, add enough hot (or boiling) water to cover the vegetables in the slow cooker.)
Serve alone or with potatoes and carrots. Serves 6-8.
Optional Homemade Seasoning Mix
Place all of the seasoning spices in a large mortar bowl and coarsely crush with pestle.You'll want to use whole spices for this mix, not ground.
Place in a covered container to use as needed. For this recipe, you'll want to use 2-3 tablespoons of the homemade seasoning mix.
Notes
*Nutrition information is based on the addition of carrots and potatoes in the dish.