Adding miso to the yolk brings salty flavors and umami notes, while Sriracha adds contrasting heat to the rich filling of this test-kitchen favorite.
In a medium saucepan, cover eggs with 1 inch of water. Bring to a boil; remove from heat. Cover and let stand 12 minutes. Drain eggs; run under cold water until cool enough to handle.
Peel and halve eggs lengthwise; remove yolks and transfer to a bowl. Mash with a fork; mix in mayonnaise, mustard, and vinegar. Press through a sieve to make smooth. Stir soy sauce, miso paste, and sriracha into yolk mixture. Press through sieve again.
Using a pastry bag fitted with desired tip (we used plain and star tips), pipe yolk mixture into whites. Garnish with black sesame seeds. Serve immediately, or chill up to 2 hours.
Instead of piping the filling with a pastry bag and tip, you can use a resealable plastic bag with a corner snipped off. Or simply spoon it into the egg whites.