Mix ingredients, refrigerate 20 minutes+ (keeps 2 weeks).
Dissolve sugar and salt in vinegar.
Heat oil in a large pot over medium heat. Add onion and cook for 2 minutes to soften, don't let it brown.
Add cabbage, vinegar, water and caraway seeds, give it a toss.
Cover, cook on low for 15 minutes, mixing once at 10 minutes.
Transfer to container (including liquid), cool until just warm. Keeps 2 weeks in the fridge.
Thinly slice still cold pastrami (Note 1). Place in a container with a couple of tablespoons of pastrami liquid (reserved from cooking, see pastrami recipe).
Microwave to warm through (or use other method of choice etc cover with foil and place in oven).
Preheat grill/broiler to medium high with shelf about 25cm/10" from heat source.
Toast bread. Spread with butter, then 1 tbsp Russian Dressing on each piece.
Pick up pastrami and let excess juices drip away, then place on bread.
Do same for sauerkraut, pile onto pastrami, then top with cheese.
Also place cheese on other slice of bread (ie with just Russian Dressing).
Place under grill until cheese is just melted. Sandwich together and devour while hot!
