Cook chicken in oil, stirring constantly.
Transfer to bowl, reserving liquid in pan.
Cook onion and garlic, then blend in flour, chili powder, pepper and cumin.
Continue cooking for two minutes and then add chicken stock, milk, chilis and tomato paste, or substitute.
Simmer on low heat until thickened, return chicken pieces to the pot and stir.
Allow to cool slightly.
Put 1/2 cup (125ml) of this mixture onto each tortilla and fold in sides, then roll up, placing seam-side down in baking pan.
Brush lightly with olive oil mixed with a little melted butter and bake at 375°F or 190°C for 10 to 15 minutes.