Sheila, I'm not sure this is a huge help, as we were last in Peru in 1995, but I'm sure you know that the "upscale" section of Lima is Miraflores, and it's pretty much an international high-end shopping area with Benneton, Gucci, the Gap, etc. Most of the higher-end Peruvian (as opposed to international) restaurants in that area should offer a taste of the country's culinary style in an upscale environment. One in particular I recall as being good and well recommended was Las Tres Brujas (the Three Witches). I may be spelling the Spanish name incorrectly, but it's close to that.
My brother, who lives in Lima, took us to a lot of places for ceviche, anticuchos and other Peruvian specialties. Are you leaving soon? If there's time, I'll ask him for a couple of current recommendations, especially if you're looking for something nice but less touristy than Miraflores.
I can't help too much with Cusco ... the nicer hotel dining rooms are very American-touristy, and my one experience there in an inexpensive, true Peruvian rosticeria did not end well: Even after having been in the country for a few weeks, I really should not have eaten the mayo that was out on the table for dipping fries in.