Heat butter in a skillet. Add leeks and saute until soft and beginning to brown. Add thyme and parsley and cook for 1 more minute.
In a large bowl, combine cheese, 1 cup of the breadcrumbs, milk, mustard, 1 of the eggs, sauteed leeks, salt and pepper. Mix well. Divide into 8 sausage shaped patties.
In 3 separate shallow bowls, place the remaining breadcrumbs, egg and flour, each in its own bowl.
Bread the sausages by rolling first in the flour, then the egg and finally the breadcrumbs.
Heat enough oil for shallow frying and fry each sausage until golden brown on all sides. Drain on paper towels.
