Here's what I did. A full day ahead of time, I poached the chicken breast in chicken stock. I used Knorr because I was being lazy (the version that comes in the little tubs), and made it double strength to impart as much flavor as possible. Usually I prepare a proper court bouillon with lots of fresh, lovely aromatics...this time I just wanted to get it done because I had been having such a hard time getting everything together. After the chicken breast was poached, I popped it into the fridge until the morning I was going to prepare the tuna sauce and assemble the dish.
On that morning I prepared the tuna sauce by draining a can of white albacore tuna in water, reserving the liquid in case I needed to thin the sauce down a bit. I place the tuna in the bowl of my mini cuisinart and rinsed some salted capers (a little less than a tablespoon-worth), and put them in as well. Then added the juice of 1/2 lemon, a little dried thyme ground between my fingers (three large pinches, less than 1/2 t.), and about 1/2 t. dijon mustard (not really enough to flavor, but to help with emulsifying the oil). I also added a little onion powder and pepper, but no salt (between the capers and tuna, there would be plenty).
After whizzing the tuna around a few times to incorpate all of the ingredients, I put it on high and began to incorporate some extra virgin olive oil. Just a drop or two at first, then after that a little more freely. The sauce tightened up nicely (I was prepared to dump in an egg yolk if necessary, but it wasn't). I'm not sure how much olive oil I put in in the end, but probably around 1/4 to 1/3 c. I didn't need the reserved tuna water either, the consistency was just right the way it was, a slightly thin mayonaise.
The chilled chicken breast was able to be sliced into nice, thin pieces (around 1/8 in., or 3 mm.) thick. I arranged those on my serving dish (majolica, with my favorite pattern: raffaelesco) begining from the center and slightly overlapping the slices of chicken as I worked out from there. Then I spooned over the tuna sauce and spread it all the way out to the edges of the chicken (I wanted full coverage for maximum flavor). Before serving, I garnished it like you see below, with some sliced roasted red pepper, capers and some parsley, (I would have also included some lemon slices, but forgot...).
I served it with a nice little salad of arugula dressed with a vinaigrette flavored with some of the "nectar" from the roasted red peppers, and grilled crostini made from a loaf of ciabatta, drizzled with olive oil and sprinkled with sea salt. A sauvignon blanc from Chile was very nice, but a nice Orvieto classico (secco) would have done even better.
