A cozy, ultra-creamy potato leek soup made effortless in the slow cooker, brightened with tangy buttermilk and finished with a silky splash of cream. Comforting yet lively, with a clean, velvety finish.
Add leeks, potatoes, broth, butter, garlic, salt, black pepper, nutmeg, and bay leaf to a slow cooker and stir to combine.
Cover and cook for 3 to 4 hours on High or 6 to 8 hours on Low until potatoes are very tender.
Remove and discard the bay leaf. Using an immersion blender, blend just until smooth (about 1 minute). Alternatively, carefully blend in batches in a countertop blender, venting the lid.
Stir in the buttermilk and cream. Taste and adjust seasoning with additional salt or cream if desired.
Ladle into bowls and garnish as desired (e.g., chives, extra cream swirl, croutons, crispy shallots).