12 cups broccoli florets, stems, and stalks cut into 1-inch pieces (about 1 large head) 3 ounces Parmigiano-Reggiano, grated 2 tablespoons lemon juice (from 1 lemon) Kosher salt and freshly ground black pepper 4 slices hearty white sandwich bread, crusts removed and cut into ½-inch dice Melt 3 tablespoons of the butter in a large Dutch oven or soup pot over medium-high heat Add the onion, celery, and garlic and cook, stirring, until the vegetables are softened but not browned, about minutes (reduce the heat if the butter begins to brown) Stir in anchovies, if using, and cook until fragrant, about 30 seconds Add the flour and cook, stirring constantly, until all the flour is absorbed, about 30 seconds Stirring constantly, slowly pour in the milk, followed by the stock Stir in the baking soda and broccoli florets and bring to a boil, then reduce the heat to maintain a simmer, cover, and cook, stirring occasionally, until the florets are completely tender and olive green, about 20 minutes Working in batches, transfer the mixture to a blender, add the Parmesan, and blend, starting on low speed and gradually increasing to high, until completely smooth, about 1 minute; add additional stock or water if necessary to thin to the desired consistency (I like mine thick) Pass through a fine-mesh strainer into a clean pot (Alternatively, use an immersion blender to puree the soup directly in the original pot.) Whisk in the lemon juice and season the soup to taste with salt and pepper Keep warm Melt the remaining tablespoons butter in a large nonstick skillet over medium-high heat When the foaming subsides, add the bread cubes and cook, tossing frequently, until golden brown on all sides, about minutes Season to taste with salt and pepper Serve the soup garnished with the croutons ...Keep warm Melt the remaining tablespoons butter in a large nonstick skillet over medium-high heat When the foaming subsides, add the bread cubes and cook, tossing frequently,... golden brown on all sides, about minutes Season to taste with salt and pepper Serve the soup garnished with the croutons