Mix bay, cider, sugar, grill seasoning and vegetable oil in the bottom of a large food storage bag, squish it all together until evenly combined. Drop the meat into the bag and move it around to evenly coat it. Let stand 10 to 12 minutes. Preheat a grill pan or indoor/outdoor grill to high.
Thinly slice 1 1/2 onions and reserve 1/2 onion whole but peeled. Heat a medium skillet over medium heat. Add 2 tablespoons butter and melt it. Add the sliced onions to the pan. Peel, core and slice the apple and add it to the onions. Season the apples and onions with salt, pepper and nutmeg. Cook the apples and onions 5 or 6 minutes, then add cooked red cabbage and combine then reduce heat to low. Set aside and keep warm.
Place meat on grill and let a bay leaf remain stuck on each steak. As the meat cooks, the heat will infuse the flavor throughout the meat. Cook steaks about 6 minutes on each side. Then, let meat rest. Discard leaves.
While meat cooks, place potatoes in a pot and cover with water, bring water to a boil then salt it. Cook potatoes 10 to 12 minutes or until tender. Drain potatoes and return to the hot pot. Mash them with sour cream, horseradish and chives and season with salt and pepper, to taste. Potatoes will be thick and spicy. If you like looser mashed potatoes, add a little milk or stock, continue to smash.
While potatoes cook, remove the red cabbage to a serving bowl and cover with foil. In the same skillet that the cabbage was cooked in, add 2 tablespoons butter. Melt butter then grate the reserved 1/2 onion with a hand held grater into the butter. Cook the grated onions 2 minutes then add flour and cook a minute more. Whisk in red wine and cook off a minute then whisk in stock and bring to a simmer. Stir in mustard and gingersnaps and season the sauce with salt and pepper. Let sauce thicken a couple of minutes.
Thinly slice the flank steak on an angle against the grain. Place a mound of potatoes on each dinner plate. Lay out some sliced flank steak along the edge of potatoes and dress with a ladle of sauer-sauce. Serve red cabbage, apples and onions alongside or in small side dishes.