1-2 teaspoon horseradish/wasabi - add one teaspoon at a time as strength varies.
mayonnaise
small bunch of parsley, chopped
relish - optional
salt & pepper to taste
Instructions
For Lily's Tuna Salad, add all ingredients in a bowl, and add enough mayonnaise to bind ingredients.
For the deviled egg filling, again add all ingredients in a bowl. Don't add all the horseradish at once. Each company can vary, so be sure to taste it before adding more. Add enough mayonnaise to bind. Don't forget to taste before assembling the sandwiches and adjust seasoning with salt and pepper.
Recipe by Asian Lifestyle Design at https://asianlifestyledesign.com/2013/07/japanese-style-sandwiches/