In a large Dutch oven over medium-high heat, cook bacon pieces, reducing heat to medium after slight shrinkage, about 6 minutes. Transfer cooked bacon to a paper towel-lined plate. Discard all but a tablespoon of the bacon grease.
Charring the ham bone is optional, but I find it imparts a unique smoky flavor which I cannot achieve simply by adding the bone to the soup while it's simmering. This step involves charring the bits of meat and fat left on the bone. Replace the Dutch oven to medium heat and add 1 tablespoon olive oil. Add the bone and allow it to heat undisturbed until it begins to crackle and pop. Use kitchen tongs to rotate the bone allowing all sides to char slightly. ProTip: This action of charring the bone adds to the amazing accumulation of flavor stuck to the bottom of the pot, and trust me the step is well worth it. Remove the bone to a plate to cool. Do NOT discard.
Add the remaining tablespoon of olive oil to the Dutch oven. Add diced celery, chopped sweet onion, Kosher salt, black pepper, and smoked paprika. Sauté for over medium or medium-low heat (you merely want to sweat the mixture, not brown) for 6 to 8 minutes until very soft. Stir in chopped garlic and cook 1 minute additional.
Add in the carrots, parsnip, and split peas. Give the mixture a good stir to coat all of the vegetables and peas and cook for 2 minutes. Cooking the peas more or less dry gives the smoky notes that have built up in the bottom of the pot a chance to flavor the tough outer layers. If substituting a russet in lieu of the parsnip, peel, dice, par-boil in salted water for 8 minutes, and drain.
Turn the heat back to medium-high and replace the ham bone to the pot. If substituting a russet in lieu of the parsnip, add the bar-boiled and drained pieces to the soup now. Add in 8 full cups of chicken broth, homemade stock or homemade bone broth. No one is wrong or better. Using stock or bone broth will offer a richer soup. Using low sodium chicken broth will accurately limit the amount of sodium.
Use the back of a wooden spoon to scrape the bottom of the pan of the accumulated brown bits known as fond. Add the bouquet garni of fresh herbs and simmer, covered, for a cooking time of 35 minutes.
Discard the bouquet garni and remove the ham bone. Use an immersion blender to puree just about half to three quarters of the soup. Use a sharp kitchen knife and CAREFULLY cut away any charred bits of ham from the bone. Add the bits to the soup along with all but a few pieces of the crispy bacon and stir.
Taste. Season with salt and pepper if required. Ladle the soup into bowls. Top with the reserved pieces of bacon, freshly torn parsley leaves, and crunchy croutons. Serve with baguette and softened Irish butter or other tasty homemade bread.