Using the same skillet, sauté the shallots for 1 minute. Add the red wine, scraping up any browned bits on the bottom of the pan. Let wine boil until reduced by half. Add stock and blackberry preserves, return to a boil and reduce by half. (The sauce should coat the back of a spoon.) Whisk in the 2 tbsp. butter. Season sauce with additional salt and pepper, to taste. To serve, drizzle the sauce over the steaks. Place a pat of compound butter and scatter a few blackberries on the plate.