Yuzu Kosho Deviled Eggs

Ingredients

• 2 Tbsp. Champagne vinegar or white wine vinegar
• 1 tsp. sugar
• 2 tsp. finely chopped shallot
• 3 small radishes, trimmed, very thinly sliced
• 18 large eggs
• Kosher salt
• 1 Tbsp. S&B hot mustard powder or 1 Tbsp. plus 1½ tsp. Colman’s mustard powder
• 1 large egg yolk*
• 2 Tbsp. fresh lime juice
• 1 Tbsp. (or more) green yuzu kosho
• 1 cup grapeseed oil or vegetable oil
• 2 tsp. finely chopped cornichon
• 2 Tbsp. finely chopped tender herbs (such as parsley, chives, shiso, or chervil), plus more for serving

Steps

1. Mix vinegar and sugar in a small bowl. Add shallot and let sit until softened, 5–10 minutes; drain.
2. Meanwhile, place radishes in another small bowl and pour in very cold water to cover (radishes should curl).
3. Place eggs in a medium pot and pour in water to cover by 3". Add a large pinch of salt and bring to a boil over high heat. Immediately cover, remove from heat, and let sit 8 minutes.
4. Run 1 egg under cold water; crack and peel. Yolk should be bright yellow and texture more chalky than fudgy. Let remaining eggs sit longer in water if needed, checking in 1-minute increments until done. Drain and rinse eggs under cold running water. Transfer to a large bowl of ice water and let sit, stirring every minute or so, until mostly cool, about 5 minutes. Carefully peel eggs, then trim a very small amount of white from top and bottom of each egg so they can stand on an end. Slice in half crosswise. Separate yolks from whites, transferring yolks to a small bowl. Place whites on a large plate.
5. Mix mustard powder and 2 tsp. cold water in another small bowl to make a paste. Scrape into a food processor; add raw egg yolk, lime juice, and yuzu kosho; pulse until smooth. Let sit 1 minute.
6. With motor running, pour in ½ cup oil, starting with a few drops at a time, then increasing to a very thin stream. Process until incorporated, then add 1 tsp. cold water. Stop processor and scrape down sides, then, with motor running, add remaining ½ cup oil in a very slow stream. Process until incorporated. Season mayonnaise with salt or up to 1 Tbsp. more yuzu kosho. Add cooked yolks to mayonnaise and pulse, scraping down sides as needed, until a very thick paste forms. Add shallot, cornichon, and 2 Tbsp. herbs to egg mixture and pulse to combine. Taste and season with more salt if needed.
7. Transfer egg mixture to a pastry bag fitted with pastry tip of choice, or a resealable plastic bag (snip one corner off to pipe), and chill.
8. When you’re ready to serve, arrange egg whites cut side down on paper towels and let drain. Turn over and pipe in a generous amount of filling. Drain radishes, pat dry, and place a slice on top of each egg, then sprinkle with more finely chopped herbs. Do ahead: Eggs can be cooked and mayonnaise can be made 1 day ahead. Cover and chill separately.