To make the cashew sauce, place the nuts in a food processor and pulse until finely chopped. Place in a small pan with the remaining sauce ingredients and heat gently for 4–5 minutes, stirring frequently to prevent sticking, until the sauce is thick and glossy.
Mix the chicken slices with the red curry paste and thread on to 4 metal skewers.
Preheat a sandwich grill and lay the skewers directly on the heat, bringing down the top plate to seal the chicken. Grill for 5–6 minutes, until the chicken is thoroughly cooked. Remove from the heat and set aside.
When the meat is cool enough to handle, push the chicken off the skewers directly into the pitta breads. Toast the breads in the cleaned sandwich grill for 1–2 minutes, or according to the manufacturer's instructions, until they are crispy and the chicken hot.
Cut each pitta in half, garnish with coriander leaves and serve immediately with a bowl of the warm cashew sauce.