How to Make It
Put the eggs in a large saucepan and cover with cold water. Bring to a boil over moderate heat, then simmer the eggs over low heat for 10 minutes; drain. Transfer the eggs to a large bowl of ice water to chill thoroughly, then peel. Cut the eggs in half lengthwise. Put the yolks in a bowl and mash lightly with a fork. Set the whites on a platter.
Heat the olive oil in a large skillet. Add the shrimp, season with salt and pepper and cook over moderately high heat, stirring, until opaque, about 3 minutes. Transfer the shrimp to a work surface and cut 12 of them in half lengthwise. Cut the remaining shrimp into 1/3-inch dice.
Add the diced shrimp to the egg yolks. Add the mayonnaise, radishes, parsley, capers, shallot and garlic, season with salt and pepper and stir to blend. Mound a rounded tablespoon of the filling in each egg-white half and top with a shrimp half. Serve at room temperature or chilled.