Chop the bacon into small pieces. Sauté it in a Dutch oven or large, lidded stock pot until it is lightly brown. With a slotted spoon, transfer the bacon to a bowl and pour off most of the fat—leave one or two tablespoons. Add the olive oil to the pan, then pour in the onions, carrots and parsnips and sauté until the onions are wilted and clear.
Add the garlic and cumin—stir, then add the split peas, 6 cups of liquid and the potatoes. Finally, sprinkle in a little of the cooked bacon to flavor the soup as it cooks. Add the bay leaves. Grate black pepper over the whole thing, stir one more time, then bring to a boil, reduce to a simmer and cover (leaving a little gap for some steam to escape).
Stir occasionally to prevent sticking, and check to ensure there is enough liquid—if the soup is getting too stiff and dry before it is soft and done, add more stock or water. It will be done in about 45 minutes.
Locate and discard the bay leaves. When the soup has cooled a bit, put half of it in the blender and purée it. (NOTE: YOU MAY NOT NEED TO DO THIS IF THE SPLIT PEAS ARE BREAKING DOWN AND THICKENING THE SOUP. WE ALMOST NEVER NEED THIS STEP.) Return the purée to the pot, mix everything together, and add in the reserved bacon. Cook for another few minutes and you are ready to serve.
Taste before salting; bacon and broth will add some salt. You can also pass the salt shaker at the table and let dinner guests season to taste.