How to Make It
Heat 1 tablespoon oil in a large, heavy-bottomed pot over medium-high. Add onion, garlic, 2 cups creminis, and 1½ cups shiitakes. Cook, stirring often, until softened, 6 to 7 minutes. Add broth, potatoes, and salt; bring to a boil. Reduce heat and simmer until potatoes are tender, 15 to 18 minutes. Stir in cream and pepper.
Heat remaining 2 tablespoons oil in a large skillet over medium-high. Add remaining ½ cup each creminis and shiitakes and cook, stirring occasionally, until golden brown, 4 to 5 minutes.
Ladle soup into bowls; top with chives and sautéed mushrooms and serve with bread.