Add passata, chicken stock and spices in a large saucepan and bring to a boil. All to boil, uncovered for 15-20 mins or until slightly thickened. Set aside.
Add chicken to a large bowl along with 1/4 to 1/3 cup of the sauce, adding extra if needed. You want the sauce to cover all of the chicken without dripping. Stir thoroughly to combine.
To make the quesadillas, spoon chicken into one half of a tortilla and top with cheese. Fold over and carefully place in a hot, oiled frying pan on medium-high heat and grill for 2-3 mins on each side or until cheese has melted. Repeat with remaining tortillas.
Cut each quesadilla into thirds and serve with the remaining sauce and sour cream to dip.
Notes
If you want this recipe to be even easier, you can replace all of the spices with a sachet of taco seasoning.
These Quesadillas are on the mild side so if you want to make them spicy, simply add extra cayenne pepper.
If you don't have any leftover or supermarket roast chicken, bake two large chicken breasts at 200°C for 30 mins and shred with two forks.