In a large skillet, cook bacon over medium heat until crisp. Remove to paper towels with a slotted spoon; drain, reserving drippings., Meanwhile, cut steak into 6 serving-size pieces; pound with a meat mallet to 1/4-in. thickness. Spread tops with mustard. Top each with 2 carrot pieces and 1 pickle spear; sprinkle with onion. Roll up each from a short side and secure with toothpicks., In a large skillet, brown roll-ups in bacon drippings over medium-high heat. Place roll-ups in a 4-qt. slow cooker. Top with mushrooms, parsnip, celery and cooked bacon., In a small bowl, whisk the soup, wine and Worcestershire sauce. Pour over top. Cover and cook on low until beef is tender, 6-8 hours. Sprinkle with parsley.