In a large bowl, combine ground beef, egg, breadcrumbs, salt, pepper, and shallot. Mix gently and let rest.

Divide mixture into four portions and shape into patties, about ¾ inch thick.

Heat a skillet over medium-high heat, add olive oil and butter, then sear patties for 5 minutes on each side.

Lower heat, add garlic and shallots, sauté for 1 minute until fragrant.

Stir in mustard, salt, pepper, and flour, then add whiskey and simmer for 3 minutes.

Pour in beef broth, bring to a boil, then stir in cream until smooth.

Return patties to skillet, spoon sauce over them, and simmer for an additional 5 minutes.

Garnish with chives and black pepper before serving.