Heat a cast iron skillet to medium-high and crisp all sides of the lardons or bacon. This can take about 10 minutes depending on the thickness of the bacon or lardon.
Once the lardons are crisp, remove from the pan and spoon out rendered fat (save it for roasting veggies later).
While bacon is cooking, shred cabbage using a food processor with a shredding attachment (or use a large knife and thinly slice). Add shredded cabbage to the pan over medium high to begin to brown. Remove from pan and place in a large bowl.
Add the bacon, celery, celery leaves, capers, dill, and parsley to the bowl.
In a small bowl, whisk olive oil, vinegar, shallot, garlic, mustard, and black pepper. Pour over cabbage mixture and toss.