Inspired by the classic Piedmontese vitello tonnato, this elegant recipe marries simply poached chicken breasts with a thick, creamy tonnato sauce of mayonnaise, tuna, lemon juice, capers, and anchovies. The tonnato is quickly made in a blender, spread on top of the chicken, and chilled for at least 12 hours or overnight. Juicy poached chicken is easily done; the key is not to overcook the meat. If they’re still a little pink in the center at the end of the cooking time, turn off the heat and leave them in the hot water bath to continue cooking slowly, until cool enough to handle. Do keep the sauce recipe nearby. It is fantastic in potato salad, over grilled vegetables, and used to make deviled eggs. And I can’t even begin to tell you how amazing it is in a tomato sandwich. Since the capers are very salty, do taste as you …