Bring the duck to room temperature, salt and pepper well inside and put the parsley (whole), butter and the peeled garlic cloves inside.
Brush the outside of the duck very carefully with olive oil (I do it by hand).
Cook in the preheated oven for 30 minutes at 220 degrees and then for 2 hours at 160 degrees. In between pecking in again and again so that the fat fries out.