Add the chicken to a bowl and pierce the skin (all over) with a knife then sprinkle the all purpose over the chicken and use your hands to evenly coat each chicken leg and set aside.
Meanwhile prepare the marinade/sauce by combining all of the ingredients together and whisking them until smooth.
Do a taste test to make sure the marinate is to suit. If not adjust accordingly
Reserve half of the marinade for the sauce/glaze and refrigerate
Pour half of the marinade over the chicken legs, you can use a bowl or zip bag. Allow the chicken to infuse overnight or for several hours. If the marinate is too thick, you will need to water it down a little (not too much) (only the half that's for the chicken). Add a ¼ cup of water if needed
Remove the chicken from the marinade and discard the rest.
Preheat the oven 200C/400F/Gas mark 6
Place the chicken on a greased grill/broil pan setup (chicken on a grate with roasting pan underneath (see pictures)
Roast the chicken for 40-45 minutes (cooking time may vary for you) until the chicken is cooked through and juices are running clear. Internal temperature is 165f (75c)
As the chicken is nearing it's finishing time, you want to brush it with the sauce that you have on reserve and return the chicken to the oven for 5-10 minutes (you can repeat this step if you wish)
Once cooked remove the chicken from the oven and re-glaze (optional) or serve the rest of the tamarind as sauce.