Return pot to medium-high heat and add remaining butter. Add flour and sugar and cook, whisking constantly, until lightly browned, about 5 minutes. Add sauce, raisins, gingersnaps, and lemon juice; return beef to sauce. Bring to a simmer, cover, and cook until slightly reduced, about 10 minutes. Thinly slice beef and arrange on a platter. Spoon sauce over top and sprinkle with bacon and parsley.