Cook corned beef and cabbage in any slow cooker by adding corned beef, the included seasoning packet, potatoes, carrots, onion and beer to the slow cooker with enough water to cover the meat and cook on low for 10 to 12 hours. When the meat finishes cooking, remove it from the slow cooker and add a head of cabbage to the broth. Cook on high for 30 to 35 minutes.
Spray the slow cooker with cooking spray and add the corned beef and included seasoning packet. Cut 4 peeled red potatoes and 4 unpeeled red potatoes into bite-sized pieces. Add the vegetables to the slow cooker, placing them around the meat. Cut an onion into wedges and add it to the slow cooker. Pour a can of beer into the slow cooker and add enough water to cover the meat and vegetables.
After cooking the mixture on low for 10 to 12 hours, remove the cooked meat and vegetables from the slow cooker and cover to keep warm. Cut 1 head of cabbage into wedges and it to the broth in the crock pot. Increase the heat to high and cook for 30 to 35 minutes or until the cabbage reaches the desired tenderness.
Serve the corned beef and cabbage with a sauce made of 2 tablespoons of Dijon mustard mixed with 1/4 cup of applesauce.