Peel the garlic cloves, cut in half, remove the green sprout in the middle. Salt and pepper them. Pierce the meat with a sharp knife and place half a clove in each slit.
Put the meat in a roasting tin with a bit of oil and place the potatoes around. Put the sliced onions in the gaps and add salt and pepper. Beat the remaining oil, lemon juice, mustard, oregano finely chopped garlic and vegetable stock cube dissolved in a ½ cup of hot water in a blender. Pour this over the meat and potatoes.