Heat a large skillet with extra-virgin olive oil over medium-high heat. Add meat and break it up with wooden spoon, cook 5 to 6 minutes. Add in carrots, celery, onions and garlic, season with salt and freshly ground black pepper, cook 7 to 8 minutes more. In a bowl combine the vinegar, sugar, Worcestershire, hot sauce, tomato sauce and stock. Pour into the pan and stir to combine. Simmer a few minutes more. Pile sloppy Buffalo filling onto buns and top with blue cheese and chopped pickles.