Prepare Marinade: In a medium pot, combine soy sauce, mirin (or sake), water, dried kelp, and sugar. Bring to a gentle boil over medium heat, then reduce heat and simmer for 2 minutes until sugar dissolves. Remove from heat and cool completely.

Separate Eggs: Carefully separate egg yolks from the whites and place in a shallow glass container in a single layer.

Combine: Strain the cooled marinade to remove kelp and pour over the egg yolks ensuring they are submerged.

Cure: Cover the container and refrigerate for a minimum of 12 hours. Flip the yolks every 12 hours to ensure maximum flavor absorption.

Serve: After curing, serve on a bowl of cooked rice drizzled with sesame oil and garnished with scallions or crushed nori.