Using the back of a spoon, gently tap eggs all over to crack shells, but don’t peel.
In a large saucepan, bring 2½ cups water, soy sauce, and brown sugar to a boil together over high heat, stirring until sugar dissolves. Add tea leaves and eggs; reduce heat to low. (If water does not completely cover eggs, add enough to do so.) Cover and simmer for 10 minutes; remove from heat. Uncover and let cool to room temperature.
Transfer eggs and poaching liquid to a medium bowl. Cover and refrigerate for at least 2 hours. (The longer the eggs stand, the deeper the flavor and the more vibrant the marbling.)
Peel eggs. Using a sharp knife, cut eggs in half lengthwise. Remove yolks from whites, and set whites aside. Place yolks in a medium bowl. Using a fork, mash until very fine. Add mayonnaise, shallot, pickled ginger and juice, Sriracha, vinegar, and dry mustard, whisking until smooth.
Transfer yolk mixture to a piping bag fitted with an open-star tip (Ateco #822). Pipe yolk mixture into egg white halves.
Garnish with pickled ginger and chives, if desired.
Notes
Lapsang Souchong is a heavily smoke-scented Chinese black tea.
Recipe by TeaTime Magazine at https://teatimemagazine.com/deviled-tea-eggs/