Melt butter in a heavy pot over medium heat. Add bacon and cook until until crisp and the fat is rendered off into the pan. Add chopped leeks and potatoes to the pan and cook until the leeks are soft.
Stir in white wine to deglaze the pan. Add stock, bay leaves and thyme and season generously with salt and pepper.
Simmer until the potatoes are very soft. Blend the soup with an emersion blender until creamy with just a few chunks. Remove from heat and cool slightly before adding the cream. Taste and season with additional salt and pepper, if needed, or a sprinkle of crushed red pepper or hot sauce, if desired.
Soup will thicken slightly as it cools.
Instant Pot: Turn instant pot to sauté. Add butter to the pot. Once melted add bacon. Once cooked, add leaks and potatoes and cook until leaks are softened. Season with salt and pepper. Deglaze pan with wine, if using. Add stock, bay leaves and thyme. Cook on manual, high pressure, for 9 minutes. Quick release and turn pot off. Blend soup lightly with an emersion blender. Stir in cream.Slow Cooker: Saute bacon in butter. Add leeks and cook until tender. Deglaze pan with wine, if using. Add everything to slow cooker along with potatoes, stock, thyme, bay leaves and salt and pepper. Cook on low for 6-8 hours or high for 3-5 hours, until potatoes are tender. Stir in cream. Taste and season if needed.Vegan: substitute plant butter or coconut oil for the butter, omit the bacon, and substitute the cream with cashew cream.Vegetarian: This soup can be made vegetarian by simply omitting the bacon and substituting vegetable broth in place of chicken broth.Gluten free: unlike some potato leek soup that is made using flour, this dish is gluten free :).Dairy free: substitute plant butter or coconut oil for the butter and substitute the cream with cashew cream.Make-ahead instructions: This soup can be made ahead and stored in the fridge for up to 3 days. If the soup is overly thick when rewarmed, add a splash of milk or cream. Taste and add additional salt, pepper, or thyme, as needed.Freezing Instructions: You can freeze leek and potato soup for up to 3 months, but don't add the cream. Allow the soup to cool, then add to a freezer safe container. Thaw in the fridge overnight or warm from frozen on the stovetop. Once warm, stir in the cream.