First, prepare the red cabbage slaw. In a bowl, combine the red cabbage, onion, carrot, garlic, 2 tablespoons of mayonnaise, 2 tbsp. wholegrain mustard and the apple cider vinegar. Set aside for 10 minutes or so to mature.
In the meantime, preheat the stove top ( either the boiling or simmering top, it will take longer to toast on the simmering top but will be more uniform).
Then, In a small bowl, combine the rest of mayonnaise and tomato relish. Set aside until needed.
To continue, Butter one side of all the bread slices.
Spread some tomato relish mayonnaise on the toasted bread.
Build the the sandwich by layering over half of the breads slices, spiced beef slices, and some cabbage slaw. Add a generous amount of cheese, and close with the other slices of bread.
Place the sandwiches in the Aga toaster tool, and add if possible a bake-o-glide liner on the cooker to keep the cooker clean of melting cheese.
Close the lid over the aga toaster and let it toast and melt for 3-5 minutes turning the rack once to ensure both sides are well coloured.
Once cooked, remove from the rack place on a board and enjoy immediately.