Onsen tamago

Prepare dashi stock: Place Kombu into 500g Water in a pot. Heat gently over medium-low heat. Just before the water boils, remove the Kombu.

Increase heat to medium-high. Once the water boils, turn off the heat and add 15g Katsuobushi. Let it steep for 30 seconds, then strain the dashi stock through a fine-mesh sieve, discarding the used Katsuobushi. You should have about 400g dashi stock.

Prepare the sauce: In a small saucepan, combine 200g of the prepared dashi stock, Koikuchi soy sauce, Mirin, and Sake. Heat gently over low heat until just warm, do not boil. Set aside.