If you don't have a steamer basket, improvise: Place a ramekin in the bottom of the pot and prop a dinner plate on top so steam can circulate around it.
Ingredients
1 teaspoon vegetable oil
1 tablespoon finely chopped peeled ginger, plus four 1/2"-thick slices
1 tablespoon reduced-sodium soy sauce
2 teaspoons fresh lemon juice
1/2 teaspoon toasted sesame oil
Pinch of sugar
2 scallions, white and green parts separated, thinly sliced
6 sprigs cilantro, leaves and stems separated
2 5-ounce skin-on firm white fish fillets (such as branzino)
Kosher salt
1 tablespoon vegetable oil
1 garlic clove, thinly sliced
1 bunch Tuscan kale, center ribs and stems removed, cut into 1" strips
1/2 teaspoon kosher salt plus more
1/2 cup kimchi, chopped (optional)
1 teaspoon toasted sesame oil
Freshly ground black pepper
Directions
Heat vegetable oil in a small skillet over medium-high heat. Add 1 tablespoon chopped ginger and cook, stirring, until fragrant, about 1 minute. Transfer ginger to a small bowl; mix in soy sauce, lemon juice, sesame oil, and sugar. Set sauce aside.
Line a large steamer basket with scallion whites, cilantro stems, and sliced ginger. Set scallion greens and cilantro leaves aside.
Using a small knife, score skin side of fish at 1" intervals; season with salt and place in steamer, skin side up. Set steamer in a large pot filled with 1" of simmering water and cover; steam fish until cooked through, 6–8 minutes.
Heat vegetable oil in a large skillet over medium-high heat. Add garlic and cook, stirring, until softened, about 1 minute. Add kale, 1/2 teaspoon salt, and 1/4 cup water. Cover and cook, tossing occasionally, until leaves are tender and bright green, about 2 minutes. Mix in kimchi, if using, and sesame oil; season with salt and pepper.
Spoon sauce over fish, top with reserved scallion greens and cilantro leaves, and serve with sesame kale.
