In cast iron skillet, heat oil and butter on medium high heat.
Brown the chicken in olive oil and butter, turning it to get an even color all over, until golden brown.
Remove from the heat, put the chicken on a plate, discard the oil left in the pot. This will leave you with tasty sticky goodness at the bottom of the pan which will give you a lovely caramel flavor later on.
Put your chicken back in the pot with the rest of the ingredients, and cook in the preheated oven for 1½ hours. Baste with the cooking juice when you remember. The lemon zest will sort of split the milk, making a sauce which is absolutely fantastic.
To serve, pull the meat off the bones and divide it onto your plates. Spoon over plenty of juice and the little curds. Serve with wilted spinach or greens and some mashed potato.