Take the chill off the steaks and preheat an outdoor grill or griddle pan to medium-high. In a pot, cover the potatoes with water. Cover the pot and bring to a boil, then uncover, salt the water and cook the potatoes until tender, about 12 minutes. Drain, then return the potatoes to the pot and crack in half with a potato masher. Pour in the consomme (or stock).
While the potatoes are working, grate the shallot into a salad bowl. Add the mustard, honey (or agave), worcestershire sauce and lots of pepper. Whisking constantly, stream in the EVOO; season with salt and pepper to taste.
In a small saucepan, melt the butter on the grill, or, if you're cooking on the stove, over low heat. Add the sage and garlic and cook, stirring, for 2 minutes. Remove from the grill or reduce the heat to low. Season the steaks with salt and pepper and grill, turning occasionally, for about 9 minutes for medium. Baste the steaks with the garlic-sage butter during the last couple of minutes of cooking. Remove from the heat and let rest, then slice.
Toss the cooked potatoes, the onion, celery and watercress with the shallot dressing; sprinkle with the blue cheese. Serve with the sliced steak on top or alongside.