Preheat the oven to 200 ° C (Th 6-7).
In a baking pan, brown the aiguillette on all sides with 10 g butter and half the oil and set aside.
Discard the fat and sweat 5 min. chopped garlic and onion, a carrot and celery cut into very small dice in the same amount of oil and margarine.
Put the aiguillette on this aromatic filling, wet with red wine and broth halfway up, bring to a boil, cover and put 1 h 15 in the oven. Make return 5 min. carrots in 20 g margarine, salt and pepper, add the crumbled thyme, pour the white wine and cook for 20 minutes. over low heat and uncovered.
Pick the marrow bones 10 to 12 min. in the remaining beef broth and then remove the marrow from the bones. Filter the cooking juices from the meat and reduce by half, then, off the heat, beat with the remaining margarine.
Serve the sliced and sauce-cut aiguillette, accompanied by the glazed carrots and slices of marrow.