Preheat oven to 275 degrees Fahrenheit.
Butterfly lamb shoulder and remove any tough sinew or fat.
In a food processor add thyme, rosemary, flat leaf parsley and garlic cloves.
Blend until finely chopped and add olive oil. Blend another 1 to 2 minutes.
Spread herb mixture on the inside of lamb shoulder and season with salt and white pepper. Roll up lamb shoulder and tie with butchers twine or kitchen string.
Place lamb shoulder in a large pot and cover with duck fat or lard.
Place on stovetop and bring to a simmer.
Place in oven for 2 to 3 hours or until lamb is cooked.
Remove from oven and allow meat to cool in fat.
To serve: Remove meat from fat. Remove string and cut lamb into medallions.
In a fry pan add a little duck fat or oil. Add lamb and lightly brown on each side. Add lamb stock.
Add medallions of lamb and place over medium heat until meat is warm and nicely coated.