Peel and finely chop the onion. Peel and grate or crush the garlic. Finely grate or pare the zest from the lime. Put the lime to one side for later. Pick the leaves off the parsley stalks. Finely chop the stalks.
Pop the onion in a deep frying pan or wok with 2 tbsp water. Season with salt and pepper. Gently cook the onion over a low heat for 5 mins till it's soft but not coloured. If it starts to catch, add a splash more water.
Add the garlic to the onion. Measure out 1 tsp of the smoked paprika and add that to the pan with the lime zest and parsley stalks. Cook and stir for 1 min.
Stir the chopped tomatoes into the pan. Half fill the tin with water. Stir that into the pan. Turn the heat up. Bring to the boil. Pop on the lid. Turn the heat down and simmer for 5 mins till the sauce is a little thicker.
Add the chicken to the pan. Pop the lid back on the pan. Simmer for 15 mins till the chicken is cooked through and the sauce is thick. Turn the chicken over a few times while it cooks.
Pop the lamb's lettuce in a bowl. Add 2 tsp olive oil and some salt and pepper. Toss to mix together.
Warm a dry frying pan. Add one of the tortillas. Warm for 30 secs till it's soft and pliable. Flip it over and warm for another 30 secs. Slide out of the pan. Repeat with three more tortillas.
Lift the chicken out of the sauce, shaking off as much sauce as possible. Use two forks to shred it. Stir it back into the sauce. Taste and adjust the seasoning. Pile the pulled chicken into the tortillas. Serve with the lamb's lettuce and lime wedges for squeezing. Scatter over the parsley leaves.