📝 About This Recipe
Originating from the volcanic Izu Islands of Japan, Kusaya is a legendary delicacy known for its pungent aroma and deep, umami-rich flavor. This traditional fermented fish is cured in a 'Kusaya-jiru'—a centuries-old brine teeming with beneficial lactic acid bacteria—before being sun-dried to perfection. While the scent is famously bold, the taste is surprisingly mellow, salty, and complex, offering a gourmet experience that has been cherished by islanders for generations.
🥗 Ingredients
Main Seafood
- 4 large pieces Fresh Blue Mackerel (Saba) or Flying Fish (extremely fresh, approximately 300g each)
The Fermentation Brine (Kusaya-jiru Base)
- 2 liters Filtered Water (unchlorinated is best for bacterial growth)
- 150 grams Sea Salt (high-quality natural sea salt)
- 200 ml Fish Sauce (Shottsuru or Ishiru) (acts as a starter culture for the brine)
- 100 ml Dried Shiitake Mushroom liquid (provides initial glutamates)
- 50 grams Sake Lees (Kasuzuke) (optional, to encourage fermentation)
For Grilling and Serving
- 2 tablespoons Japanese Sake (for brushing during grilling)
- 1/2 cup Grated Daikon Radish (to cleanse the palate)
- 1 whole Lemon Wedges (cut into 4-6 pieces)
- 1 teaspoon Shichimi Togarashi (Japanese seven-spice for a kick)
👨🍳 Instructions
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1
Begin by cleaning the fish. Scale the mackerel thoroughly and remove the head if desired, though traditional Kusaya often keeps the head on. Split the fish down the back (back-opening style) to butterfly it, keeping the belly intact.
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2
Remove all internal organs, gills, and the black membrane inside the cavity. This is crucial as any remaining blood or guts will cause spoilage rather than fermentation.
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3
Rinse the butterflied fish under very cold running water for at least 5 minutes to remove all traces of blood. Pat extremely dry with paper towels.
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4
Prepare the brine by mixing the filtered water, sea salt, fish sauce, shiitake liquid, and sake lees in a non-reactive container (glass or food-grade plastic).
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5
Submerge the fish completely in the brine. Use a fermentation weight or a heavy plate to ensure no part of the fish is exposed to air.
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6
Allow the fish to ferment in a cool, dark place (ideally 15-18°C) for 12 to 20 hours. If your kitchen is warm, use the refrigerator, but extend the time to 24-30 hours.
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7
Remove the fish from the brine. Do not rinse them. The 'stink' at this stage is normal and indicates the lactic acid bacteria are working.
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8
Arrange the fish on a bamboo drying rack (zaru). Place them in a sunny spot with excellent airflow. If birds or insects are a concern, cover with a fine mesh net.
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9
Dry the fish for 1 to 2 days. The surface should be dry to the touch, slightly translucent, and firm, but the meat should still have a hint of flexibility.
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10
Once dried, the Kusaya can be wrapped tightly and refrigerated for a week or frozen for longer storage.
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11
To cook, preheat a Japanese fish grill (broiler) or a cast-iron pan over medium-high heat. Lightly brush the skin side with sake.
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12
Grill the fish meat-side down first for about 3-4 minutes until lightly browned. Flip and grill the skin side for another 2-3 minutes. Note: The aroma will be very intense during cooking—ensure your kitchen is well-ventilated!
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13
Remove from heat and immediately tear the flesh into bite-sized strips while hot, as this is when the texture is best.
💡 Chef's Tips
Use the freshest fish possible; any hint of 'old fish' smell before fermentation will ruin the final product. If you don't have a traditional starter brine, using a high-quality 'Shottsuru' (Japanese fish sauce) provides the necessary microbes to kickstart the process. For the drying phase, a small electric fan can be used indoors if you don't have a suitable outdoor space with a breeze. To reduce the intensity of the smell when grilling, you can wrap the fish in parchment paper or foil, though you will lose the charred texture. Never overcook Kusaya; it should remain slightly chewy and moist in the center, not bone-dry.
🍽️ Serving Suggestions
Pair with a dry, chilled Junmai Ginjo Sake to cut through the saltiness and complement the umami. Serve alongside a bowl of hot steamed white rice or as 'Ochazuke' (poured over with green tea). A side of cold, crisp cucumber slices or pickled ginger helps balance the heavy fermented flavors. Enjoy as a 'Chinmi' (rare delicacy) snack while drinking Japanese Shochu on the rocks. Top with a squeeze of fresh Sudachi or Lemon to brighten the deep, earthy notes of the fish.