Heat a cast iron frying pan over medium heat, fry the pancetta, turning frequently, until crisp. Remove the pancetta pieces and drain on paper towels.
Leaving the fat in the pan, add your potatoes. (If you skipped the pancetta, add 2 tablespoons of olive oil.) Spread the potatoes evenly over the pan, let sit for a few minutes. Season with salt and pepper, then move them around. Let sit again for a few minutes, move around again, and continue until the potatoes are mostly browned and mostly crisped - probably about 12-15 minutes. Add your onions and cook for 5 minutes, stirring occasionally. Add your asparagus, cover the pan, and cook for 5 to 8 minutes, until crisp. Remove the lid, re-add the pancetta, and cook for one more minute. All done!
If you want, fry up an egg or two and serve them on top of the hash. Enjoy!