1) Cook the olive oil, sesame oil, red onion, garlic, ginger, and red chilli flakes in a small, heavy-bottomed pot on medium heat until the onion is transparent, 10 to 15 minutes.
2) Whisk in the vinegar, sugar, soy sauce, peanut butter, ketchup, sherry, and lime juice; cook for 1 more minute. Cool.
3) Using a sharp knife, carefully remove the entire breast of the rotisserie chicken and slice it diagonally in 1cm thick slices.
4) Skewer the chicken slices with wooden sticks and serve with the sauce. Reserve the remaining chicken.