Whisk fish broth and curry paste in a stock pot; cook until warm, set aside.
Heat two tablespoons oil in a large cast iron skillet. Season sea bass with salt and pepper; add to skillet and cook until seared on one side. Flip and continue cooking until no longer opaque inside. Remove and rest fish.
Add remaining oil to the skillet and place sliced cauliflower directly on hot pan, using remaining salt and pepper to season. Flip and cook until both sides have been charred.
Arrange fillets in wide serving bowls. Arrange equal portions charred cauliflower next to fish. Top with 1/4 cup steamed sea beans. Ladle in warm broth.
Garnish with lemon grass leaves and fennel fronds.