White Borscht Soup

Name: White Borscht Soup
Ingredients: 3 tablespoons (42 grams) unsalted butter; 1 medium white onion (240 grams/3 cups), roughly chopped; 2 leeks (180 grams/2 cups), white parts and an inch or 2 of green, sliced thin and rinsed; 2 small carrots or parsnips (180 grams/1 1/2 cups), roughly chopped; 2 stalks celery (180 grams/1 1/2 cups), roughly chopped; Kosher salt; Couple turns of black pepper; 2 cloves garlic, roughly chopped; 1 pound Yukon gold potatoes, cut into 1/2-inch dice; 6 cups (1440 grams) low-sodium chicken broth; 1 bay leaf; 1 pound smoked kielbasa, kept whole; 4 ounces sourdough bread, cut or torn into 1-inch cubes (about 2 cups); use the rest of the loaf for serving; 1/4 cup (60 grams) dill pickle brine; Sour cream, for serving; Dill pickles, chopped up, for serving; Fresh dill, for serving