Combine seaweed, garlic, peppercorns and water in a large sauce pan and bring to a boil. Lower heat and simmer about 20 minutes. Strain and return the liquid back to the pot. Add both soy sauces, bring back to a boil and cook until mixture is reduced and almost unbearably salty. Remove from heat and stir in miso.

Pour into a bottle or jar and keep in the refrigerator. Use one-for-one to replace fish sauce in vegan recipes.