Sauce: Heat oil in a heavy saucepan. Add onions, garlic, carrots, celery, bay leaves, and peppercorn to the hot pan and sauté over medium-heat for about 5 minutes, stirring occasionally until golden brown. Deglaze pan with the wine and add the stock, mustard, and honey.
Reduce liquid to about 2 1/2 cups, stirring constantly until the sauce is thick enough to coat the back of a spoon.
Strain through a finemesh sieve into a clean saucepan (discard the solids) and return to the heat. Whisk in the butter, a little at a time, and mix thoroughly.
Keep the sauce warm over hot water in a double boiler.
Onions: Heat oil in a deep fryer or heavy saucepan (there should be enough to come at least 1 1/2 inches up the sides of the pan).
Place flour on a plate and lightly dredge the onions in the flour.
When the oil is hot, fry the onions for about 7 minutes over medium-high heat, turning constantly but gently, until golden brown.
Drain on paper towels, and keep warm.
Season the steaks with salt and pepper. Grill for 6 minutes per side for medium-rare or about 7 minutes per side for medium.
Place a steak in the center of each warm serving plate and spoon the sauce around the meat.
Place a handful of the onions on top of each filet and the rest on the side. Serve immediately.