Hard-boil the eggs (this method makes them perfect):
Combine 1 dozen eggs, fresh from the fridge, and 3 quarts cold water in a large saucepan. Bring to a boil over medium-high heat, turn off the heat, cover the pot and let sit for 12 minutes. Meanwhile, prepare an ice bath in a large bowl (use about 75% ice and 25% water). Drain the eggs, transfer to the ice bath and let cool completely, about 15 minutes. Peel the eggs and roughly chop them to desired sized pieces for your salad.
Marinate the shallot:
While the eggs cook and cool, whisk 1 shallot, 2 Tablespoons vinegar, 1 Tablespoon mustard, 1 teaspoon salt, ⅛ teaspoon black pepper and a pinch cayenne pepper together in a small bowl and let sit as eggs finish cooking and cooling. Marinating the shallots in vinegar helps bring down the raw-onion sting.
Finish up!
In a large bowl, mix the eggs, shallot mixture, ½ cup mayonnaise and 2 Tablespoons capers until thoroughly combined. Taste, and add more salt, black pepper or cayenne at this time.
Dry 8 radishes on paper towel, if needed.
If making a sandwich, place one large lettuce leaf or handful of spinach on half the slices of bread.
Divide the egg salad evenly over the lettuce covered bread halves, layer with radishes and olives.
Cover with remaining bread.
For salad, serve on bed of lettuce or spinach, or just plop it on your plate and devour!