Combine all tuna salad ingredients and blend well.
For the sliders...
Preheat oven to 350 degrees.
Layer the party rye with piece of muenster, piece of Havarti, scoop of tuna salad, egg slice, tomato slice, piece of muenster, piece of Havarti and top with bread slice. Repeat.
Melt butter in a skillet and grill sliders on both sides until golden brown and cheese has melted. Remove to a baking pan. Once all sliders have been grilled, transfer to oven for 7-10 minutes.