Crispy Tofu in Shiitake Broth

Name: Crispy Tofu in Shiitake Broth
Ingredients: 1/4 cup plus 2 tablespoons reduced-sodium soy sauce; 1 tablespoons light brown sugar; 1 (12-ounce) package firm tofu, drained; 3 scallions; 12 shiitake mushrooms, rinsed, patted dry; 2 (4x3-inch) pieces dried kombu; 1 (3-inch) piece ginger, peeled, thinly sliced; 4 garlic cloves; 2 tablespoons vegetable oil; Kosher salt; 4 baby bok choy (about 12 ounces total), halved lengthwise; 2 medium carrots, peeled, thinly sliced into rounds; 1 small radish, trimmed, thinly sliced into rounds; Toasted sesame oil (for serving)