Slice the leeks, discarding the thick green pieces that are at the ends. Important to rinse the leeks AFTER slicing, they can sometimes have sand in them. Add to a large skillet with the butter and garlic and cook over medium-high heat until the leeks are softened and browned.
Add to the crock pot along with the potatoes (peeled if you prefer), bay leaves, thyme, salt and pepper.
Add the chicken broth and close the lid. Cook on high for 5 hours or low for 8 hours.
Once the potatoes have softened enough, remove the thyme (if using fresh sprigs) and bay leaves. Use an immersion blender (or food processor or blender) to blend the soup. DO NOT overblend. If you are using a food processor or blender, blend the soup in small batches.
Add the cream, blend again a little, then top with chives for garnish. Serve hot with crusty bread.
Video
Notes
Half and half or milk can be used instead of cream but won't have such a rich flavor.Russets are fine to use if that's all you have on hand. We prefer the buttery texture of the Yukon gold potatoes.