Begin with Onions: Heat 2 tablespoons of olive oil or butter in a large pot over a medium-high flame. Once hot, introduce the diced onion to the pot, stirring occasionally until it reaches a golden hue, approximately 5 minutes.
Garlic Time: Add the rough-chopped garlic cloves to the onions, continuing to stir for another 1-2 minutes until the aroma of garlic fills the air.
Add Main Ingredients: Into the pot, incorporate the sliced celery and potatoes, along with the vegetable or chicken broth, a cup of water, a bay leaf (optional), salt, pepper, and a bit of cayenne for heat. Adjust the liquid level so it just covers the vegetables. Cover the pot, bring the mixture to a boil, then lower the heat for a gentle simmer until the potatoes soften, which should take about 10 minutes.
Herb Integration: After turning off the heat, discard the bay leaf and gently mix in the fresh dill and parsley, allowing them to just slightly wilt. This step is crucial for maintaining the herbs' vivid color and fresh flavor.
Blending for Smoothness: Using an immersion blender, process the soup until it achieves a very silky and smooth consistency. If a regular blender is your tool of choice, let the soup cool slightly before blending in small portions. Remember, if blending warm soup, only fill the blender halfway to prevent pressure buildup and start blending at the lowest speed, gradually increasing to avoid splashes.
Reheat and Enrich: Pour the blended soup back into the pot and warm it over a low flame. Now's the time to mix in your chosen cream option, stirring gently to avoid boiling and preserve the soup's vibrant green hue.
Garnishing for Elegance: For crispy celery leaf garnishes, heat a generous amount of olive oil in a skillet over a medium setting. Test the oil's readiness with a single celery leaf, frying it for 10-20 seconds on each side until crisp. Fry the remaining leaves in small batches, ensuring they don't overcrowd the skillet. Lastly, briefly fry nigella seeds in the same oil until they start to pop, then use them to adorn the soup along with the crispy leaves and optional hemp seeds for an extra touch of flavor and texture.