In a large skillet, heat up a tbsp. of vegetable oil and add the diced pancetta in. Cook until they're starting to brown on the outside, about 5 minutes.
At this time, throw in the shallots and cook until tender, about 2 minutes. Add the shaved brussel sprouts to the pan and stir around. Add the apple cider vinegar on top, as well as the salt and pepper.
Continue to cook down the brussel sprouts until they're soft and tender, about 10 minutes.