Add <quantity>½<unit>cup</unit></quantity> of brown sugar to a large stock pot

Add <quantity>1<unit>cup</unit></quantity> of wild blueberry raisins

Add <quantity>2<unit>cups</unit></quantity> of dry shiitake mushrooms

Add <quantity>⅓<unit>cup</unit></quantity> of soy sauce

Add <quantity>2<unit>sheets</unit></quantity> of <quantity>4<unit>inches</unit></quantity> x <quantity>8<unit>inches</unit></quantity> kombu seaweed

Add <quantity>5<unit>L</unit></quantity> of water

Bring to a boil and let the stock simmer over low heat for 6h until the flavor is concentrated and the liquid coats the back of a spoon. Strain. The mushroom reduction is ready

Make an incision behind the fin closest to the head of <quantity>1</quantity> mackerel. Carefully slide the knife along the backbone, separating the side from the bones. Repeat this on the other side of the mackerel

Cut along both sides of the bones to separate the belly from the fillet

Trim the ends of the fillets

Place the mackerel on <quantity>2</quantity> sheets of kombu seaweed and cover it with <quantity>2</quantity> additional sheets. Let it sit for 3h to cure and season

Cut <quantity>1</quantity> black garlic head in half and add to a saucepan

Cut <quantity>1</quantity> garlic head in half and add to the saucepan

Add <quantity>2<unit>cups</unit></quantity> of grapeseed oil

Warm over medium heat until the garlic starts to bubble

Turn the heat to low and cook for 2h to infuse the oil. The garlic oil is ready

Add <quantity>½<unit>cup</unit></quantity> of brown butter to a saucepan

Add <quantity>2<unit>tbsp</unit></quantity> of the Garlic Oil

Add <quantity>¼<unit>cup</unit></quantity> of the Mushroom Reduction

Add <quantity>2<unit>sheets</unit></quantity> of <quantity>2<unit>inches</unit></quantity> x <quantity>8<unit>inches</unit></quantity> kombu seaweed and warm over medium heat to infuse. The brown butter & mushroom sauce is ready

Brush both sides of the mackerel with the Brown Butter & Mushroom Sauce

Grill the mackerel, skin-side down, for 3m until the skin is crispy

Flip the mackerel and grill for 2m until cooked through. Remove from the heat

Transfer the mackerel to a cutting board, skin-side up. The grilled mackerel is ready

Enjoy this savory, rich fish!