Preheat the BBQ grill to medium heat. Place an ovenproof saucepan directly over the BBQ grill.
Add butter to the pan; when it begins to foam, add garlic and chilli; cook, stirring continuously, until aromatic; remove from heat and add the sake. (Ensure sake is poured away from direct heat, so it doesn’t flame up.)
Return to heat and reduce by half; add tamari, lemon juice and fish stock, and boil. Combine cornflour and water, stir into mixture and return to a spot; cook until sauce
thickens; add parsley, salt and pepper, mix well and set aside.
For the mussels, increase the heat on the BBQ grill to medium-high; grill mussels, in 2 batches, for about 3 minutes or until they open. (Discard any mussels that don’t open.) Transfer to a large bowl; pour over the sauce and toss to combine. Serve with lemon wedges and spring onions.
Mussels are sold and cooked live; tap shells are to test their freshness. Those that don’t snap shut are no longer living and need discarding. They spoil and may ruin your dish.
Mussels are easy to clean: scrub them well under cold running water and remove the ‘beard’ by firmly grasping and pulling away the fibrous clump of hair-like fibre.
Although highly perishable, mussels can be stored in a bowl in the fridge for up to 3 days.