In a large mixing bowl, combine well-drained sardines, breadcrumbs, and diced vegetables. Season with herbs and spices, mixing until a thick paste forms. This takes about 5 minutes.

Divide the mixture into 2-3 equal portions, shaping each into patties about 1 inch thick, creating a well in the center.

Place the patties on a parchment-lined plate and refrigerate for 10-15 minutes.

Carefully remove the patties from the refrigerator and place a yolk in the well of each patty.

Heat oil in a skillet over medium heat, and cook patties yolk-side up for 6-8 minutes until golden brown.