Add the shallots and cook, stirring often, until softened but not brown, about 2 minutes. Now comes the magical red wine sauce. Pour in the Pour in the wine and stir, scraping any sticky bits off the bottom of the pan. Stir in garlic and cook for an additional minute. Place the hot pan back on the stove and brown the onions. Stir in the flour and cook to a sandy paste, then splash in the vinegar and simmer for a moment. Turn down the heat and fry the chopped shallots in the butter until softened, about 2 minutes. In a medium sauté pan, heat 1 Tbs. Pour the fat out of the pan you cooked your steaks in, but don’t clean it. Place the pan back on the heat with half the butter and the shallots and sizzle for 2 mins to soften. Boil until reduced to 1/2 cup, about 9 minutes. of the butter over medium heat. Add a dry red wine and start scraping up the bits on the bottom of the pan. Add the broth, wine, vinegar, and mustard. Increase the heat to high and bring to a boil, stirring frequently. After removing the steaks from the oven, transfer them to a serving platter to rest while you make the red wine sauce.