Set a large 6-8 quart soup pot over medium heat. Add the butter, chopped onions, garlic, and chopped celery. Add 1 teaspoon salt and ¼ teaspoon ground black pepper. Stir and soften the vegetables for about 10 minutes. Make sure everything is very soft, without browning. If needed, turn the heat down to medium-low.
Once the veggies are very soft, add in the bay leaf, chopped dill, and vegetable broth. Simmer for 15-20 minutes, stirring occasionally.
Remove the bay leaf. Pour the soup into a large blender. Secure the lid. Open the top vent and cover the lid with a towel for safety. Puree the soup. *You can puree it until completely smooth, or leave it slightly chunky, based on your preference. You can also leave the soup in the pot and puree with an immersion blender if desired.
Pour the soup back into the soup. Stir in the heavy cream. Taste, then salt and pepper as needed.
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Notes
This soup is vegetarian unless chicken broth is used. Use plant-based butter and cream for vegan.Leftover soup will keep well for up to 5 days in the refrigerator. Let the creamy soup cool to room temperature, then transfer to an airtight container and store in the fridge.You can also freeze! Once the soup has cooled to room temp, transfer to an airtight container or freezer-safe zipper bag (with all air removed). Keep the celery soup in the freezer for up to 3 months.