Add all meatball ingredients except the oil to a large bowl and knead until evenly combined. Roll about 2 teaspoons of mixture into firm balls; chill 5-10 minutes if needed.
Heat oil in a wide, deep skillet. Brown meatballs on all sides for 6-8 minutes, then remove.
Melt butter in the skillet. Whisk in flour and cook until medium brown. Gradually whisk in beef broth, simmer until thickened, then whisk in milk, mustard, and jelly. Simmer gently about 1 minute and season.
Return meatballs to the gravy and warm gently until heated through. Serve immediately.