Step 1

Combine water, sake, soy, mirin, and sugar in a medium bowl and whisk until sugar is dissolved, or use an equal amount of chashu broth instead. Set aside.

Step 2

Bring 2 quarts of water to a boil in a medium saucepan over high heat. Pierce fat end of each egg with a thumbtack to make a tiny hole (this prevents them from cracking and eliminates the air bubble at the end). Carefully lower eggs into water with a wire mesh spider or slotted spoon. Reduce heat to maintain a bare simmer (about 190°F). Cook for exactly 6 minutes. Drain hot water and carefully peel eggs under cold running water (the whites will be quite delicate).

Step 3

Transfer eggs to a bowl that just barely fits them all. Pour marinade on top until eggs are covered or just floating. Place a double-layer of paper towels on top and press down until completely saturated in liquid to help keep eggs submerged and marinating evenly. Refrigerate and marinate at least four hours and up to Discard marinade after 12 hours. Store eggs in a sealed container in the fridge for up to 3 days. Reheat in ramen soup to serve.