Rinse mussels under cold water and scrub shells. Remove beards by pulling toward the hinge. Discard any mussels that are cracked or remain open after a firm tap. Place a large pot over medium-high heat with 1/4 cup water and 1 tsp kosher salt. Add mussels, cover, and steam 4–6 minutes until shells open. Transfer opened mussels to a bowl, reserve about 1/2 cup of the steaming liquid, and set mussels aside to cool slightly. Discard any mussels that did not open.

When cool enough to handle, halve larger mussels in their shell if desired so each shell holds a single mussel with room for sauce (optional). Season lightly with 1/2 tsp black pepper distributed among shells.

Coconut cream sauce

Prepare base sauce

In a small saucepan over medium heat, melt 2 tbs butter. Add 1 finely minced shallot and 1 minced garlic clove and sweat gently 2–3 minutes until translucent and fragrant but not browned.

Build sauce

Add 1 cup coconut cream to the pan along with 1 tsp fish sauce, 1 tbs lime juice, 1/2 tsp light brown sugar, 1/4 tsp red chili flakes, 1/4 tsp salt, and 1/4 tsp freshly ground black pepper. Stir and bring to a gentle simmer. Reduce heat to low and simmer 3–4 minutes so flavors meld and the sauce slightly thickens. Taste and adjust with more lime, fish sauce, or salt as needed.

Finish sauce

Remove sauce from heat and stir in 2 tbs finely chopped fresh cilantro. If the reserved mussel steaming liquid is needed to thin the sauce, add up to 2 tbs. Keep warm until ready to assemble.

Crispy shallots & finishing

Make crispy shallots

Heat 1 cup neutral oil in a small saucepan or shallow pan to 325°F (160°C) or until a thin slice of shallot sizzles gently. Fry the 2 thinly sliced shallots in batches for about 2–3 minutes until golden brown and crisp. Use a slotted spoon to transfer to a paper towel-lined plate and season immediately with a pinch of salt. Reserve about 2 tbs of the crispy shallots for garnish and chop the rest coarsely to mix with panko.

Toast panko

In a dry skillet over medium heat, toast 1/2 cup panko breadcrumbs until light golden, stirring frequently, about 3–4 minutes. Remove from heat and stir in the chopped crispy shallots. If desired, stir in 1 tsp chili oil for a touch of heat and color.

Assemble and bake

Preheat broiler to high (or oven to 450°F/230°C if broiling is not available). Arrange the steamed mussels on a rimmed baking sheet or in a shallow ovenproof dish, keeping each mussel in its half shell and evenly spaced. Spoon about 1 rounded teaspoon of the warm coconut cream sauce over each mussel (use more for larger shells). Sprinkle a light layer (about 1/2 tsp) of the panko-shallot mixture onto each sauced mussel.

Place the baking sheet under the broiler 3–5 inches from the heat source and broil 2–4 minutes until the topping is golden and crisp and sauce is bubbling. Watch closely to prevent burning.

Finish and serve

Remove mussels from the oven. Garnish with the reserved whole crispy shallot pieces and 1 tbs fresh cilantro leaves scattered over the platter. Serve immediately with lime wedges on the side for squeezing and additional chili oil if desired.