Cook 2 strips chopped thick-cut bacon in vegetable oil over medium-high heat until almost crisp. Add 1 thinly sliced onion; cook until softened. Add 1 pound parsnips (peeled and cut into 2-inch pieces), 2 sliced celery stalks, and salt and pepper. Cook until lightly browned, 5 minutes. Add 1 1/2 cups chicken broth;simmer until mostly reduced, 10 minutes. Add a little water; stir in 1 tablespoon butter, some chopped parsley and thyme, and salt and pepper.