In a 3-quart saucepan, melt butter over medium-high heat until foaming. Add onion, and celery. Sauté until softened, about 10 minutes.
Stir in flour and cook until lightly browned, about 1 minute. Whisk in 2 1/2 cups broth and bring to simmer.
Simmer until veggies are tender, about 10 to 12 minutes longer. Transfer to blender and puree until smooth.
Wipe out saucepan. Return pureed soup to pan. Add remaining 1 1/2 cups chicken broth and cream. Bring to simmer and stir until heated through.
Season to taste with salt and white pepper. Garnish with croutons if desired.
Celery: You'll need 4 cups of chopped fresh celery. Seek out heads of celery that are full of firm, tightly-packed, medium-thick stalks. The leaves should be bright green. Steer clear of any bunches of celery with rubbery stalks, discoloration, or spotting.
Chicken broth: Store-bought or homemade Chicken Broth; choose your favorite. For a vegetarian Cream of Broccoli Soup, trade in vegetable broth.
Croutons: For a satisfying crunchy element, I like to top each bowl with a few croutons. You can buy them at the supermarket, or to make homemade croutons, slice or tear 1 loaf of bread into 1/2-inch pieces. Preheat the oven to 450 degrees. In a small bowl, whisk together 1/4 cup olive oil, 1 teaspoon garlic powder, 1 teaspoon Italian seasoning, and 1/4 teaspoon salt. In a large bowl, add the bread pieces and the olive oil mixture, then toss to combine. Spread the croutons on a parchment paper-lined rimmed baking sheet. Bake until golden brown, or for about 10 to 15 minutes.
Yield: This recipe makes eight 1-cup servings, perfect for a lunch main dish or a dinner starter.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: The soup can be made up to 3 days in advance and reheated on the stove. Garnish with croutons just before serving.
Freezer: Cream of celery soup is great for the freezer! Cool soup completely, then divide into freezer-safe containers (I love pint-sized glass mason jars). Leave 1/2-inch head space for expansion, then date, label, and freeze for up to 3 months. Thaw overnight in the refrigerator.
Take your bowl over the top: No need to limit yourself to croutons as the solo garnish. Save a few celery leaves to use as a topping, or top each bowl with a spoonful of crumbled crispy bacon or plain Greek yogurt or sour cream.