In a large pot, saute 1 onion, finely chopped, in 2 Tblsp olive oil, until the onion is soft. Add 1 celery stalk, thinly sliced, and 2 carrots, thinly sliced, and saute until the carrots are tender. Add 1 clove garlic, minced, and saute for 1 minute longer.
Add the peas, 6 slices of bacon and 1 bay leaf and bring to a simmer. Reduce heat to medium-low, cover partially and cook until peas are soft, about 1 hour, stirring occasionally.
Remove and discard the bay leaf. Remove the bacon, cut into small pieces and set aside.
If you're using a blender or food processor, allow the soup to cool before blending. If you're using an immersion blender, you can (carefully!) blend it while it's still hot. Puree the soup until it's smooth and creamy. If you prefer your split pea soup with chunks, set aside some of the solid portion of the soup before pureeing, then add the reserved peas back into the soup afterward. Return the soup to the pot, if necessary, and reheat.
Season to taste with salt and pepper, then add the bacon pieces. Serve immediately.