Melt reserved bacon drippings in a large Dutch oven. Add onion, carrots, salt, pepper, and oregano, and saute over medium high heat until al dente, about 10 minutes. Add garlic and continue to cook 1-2 more minutes, until garlic is fragrant. Can deglaze with 1-2 Tbsp white wine or additional broth if needed.
Meanwhile empty the can of Northern beans (with juice) into a small food processor or blender and puree until smooth.
Add the pureed beans, split peas, and bay leaves to the Dutch oven, then gradually add the stock, stirring constantly as you pour to remove clumps.
Turn heat down to low, cover, and cook 30-45 minutes, or until everything is tender. Remove the lid, skim any foam or pea skins, and stir a couple of times during the cooking, making sure it's still at a low boil and adding additional chicken stock/broth if it's getting too thick for your liking.
While the soup is cooking, preheat the oven to 400 degrees. Cover 2 rimmed baking sheets with foil and place a cooling rack inside each foil lined baking sheet. Spread the bacon slices out evenly across the cooling racks and bake for 15-20 minutes or until crispy. Once bacon has cooled, break into pieces for garnishing the soup.
When the soup is done cooking, turn off the heat, remove the bay leaves. Topped with crumbled bacon, sour cream, and fresh parsley, and serve with crusty bread.