Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
     1/4  cup           onions -- chopped
     1/4  cup           celery -- chopped
     1/4  cup           bell peppers -- chopped
   2      tablespoons   unsalted butter
   1      teaspoon      salt
   1      teaspoon      white pepper
     3/4  teaspoon      black pepper
     3/4  teaspoon      minced garlic
     1/2  teaspoon      dry mustard
     1/2  teaspoon      ground cayenne
   4      pounds        boneless sirloin roast

Preparation:

In a small bowl combine the onions, celery, bell peppers, butter and seasonings, mix well. Place roast in a large roasting pan, fat side up. With a large knife make 6 to 12 deep slits in the meat (to form pockets) down to a depth of about 1/2 inch from the bottom; do not cut all the way through. Fill the pockets to their depths with the vegetable mixture, reserving about 1 tablespoon of the vegetables to rub over the top of the roast. Bake uncovered at 300F until a meat thermometer reads about 160F for medium doneness, about 3 hours. For rarer roast, cook until thermometer reads 140F. Serve immediately topped with some of the pan drippings if you like. From Paul Prudhomme's Louisiana Kitche