With only six ingredients, you can create a fork-tender Pot Roast and a side of au jus packed with flavor.
Press pepper evenly onto all surfaces of beef roast. Heat oil in stockpot over medium heat until hot. Place pot roast in stockpot; brown evenly. Pour off drippings.
Add broth and 2 cups of leeks to stockpot; bring to boil. Reduce heat; cover tightly and simmer 2 to 3 hours or until roast is fork-tender.
Remove roast; keep warm. Skim fat from cooking liquid. Bring liquid to a boil and reduce for 5 minutes. Combine cooking liquid and remaining 1 cup leeks in stockpot. Reduce and simmer, uncovered, 6 to 8 minutes or until leeks are tender. Stir in mustard; remove from heat. Carve roast into slices. Serve with au jus.