Ajitama are Japanese soft-boiled marinated ramen eggs with slightly firm whites and luxuriously silky, custard-like yolks. Soaked in a sweet-savory soy marinade, they're the ultimate ramen topping...or an irresistible snack!
Bring a pot of water to boil in a medium saucepan, then add the baking soda.
Take the eggs out of the refrigerator 10-15 minutes before cooking. Gently lower them into the boiling water using a large spoon or soup skimmer and cook for exactly 7 minutes.
Transfer the eggs into an ice bath (equal parts ice and cold water) and chill for 3 minutes.
Peel the eggs, then combine the water, Chashu seasoning liquid, and mirin in a bowl or container with a tight-fitting lid.
Place the peeled eggs in the seasoning liquid and cover the top with a paper towel to help the liquid reach the eggs evenly all around.
Sprinkle the bonito flakes (if using) on top of the paper towel.
Cover and refrigerate overnight.
Remove the eggs from the seasoning liquid after 24 hours. Do not leave them in longer or they will become too salty!
Store in an airtight container in the refrigerator for up to 3 days.