Step 1

Place noodles in a large bowl and add cold water to cover; let soak 15 minutes. Drain.

Step 2

Meanwhile, combine dashi, mirin, and soy sauce in a medium bowl.

Step 3

Place thinly sliced scallions in a small bowl and add cold water to cover. Soak until they begin to curl, 8–10 minutes. Drain; squeeze to remove excess water.

Step 4

Lay cabbage in a large donabe or Dutch oven. Arrange clams, shrimp, snapper, chicken, tofu, mushrooms, carrot, 2" scallion pieces, and noodles on top; add dashi mixture.

Step 5

Cover donabe and heat over medium-high until liquid is just simmering. Uncover, reduce heat to low, and gently simmer until clams open and chicken and fish are cooked through, 5–8 minutes.

Step 6

Serve topped with drained scallions.