Herb butter: In a small bowl cream together the butter, chives, parsley, tarragon, mustard, and salt and pepper to taste. Let the butter stand, covered, in a cool place for 1 hour to allow the flavors to develop.

"French" the chicken wing bones by scraping the meat off the bones with a sharp knife (reserve the meat for another use). Detach the fillet strip from each breast, and flatten the breasts and the fillets between sheets of dampened wax paper until they are about 1/4 inch thick.

Arrange the chicken breasts skinned side down on a work surface. In the center of each, mound 2 tablespoons of the herb butter, and cover with a fillet strip. Fold up the sides of the breasts to enclose the herb butter, forming the chicken into a "chop".

Dredge the chops carefully in the flour, shaking off the excess, dip them in the egg mixture, and dredge them in the bread crumbs, patting the crumbs onto the flesh. Arrange the chops on a rack set over a pan and chill them, uncovered, for at least 1 hour or overnight to let the crumbs dry.

In a large heavy skillet, heat the oil over moderate heat until it is hot but not smoking. Brown the chops, transferring them as they are browned to a baking pan. Bake them in a preheated 350-degree oven for 20 minutes. The chicken may be kept warm, covered loosely, for up to 10 minutes.