Beef Stroganoff

Ingredients

For 4 servings

• 1 ½ pounds sirloin steak (ribeye, or filet mignon)
• 1 teaspoon kosher salt (divided)
• ½ teaspoon black pepper (divided)
• 1 tablespoon olive oil
• 1 tablespoon unsalted butter
• 1 cup diced yellow onion (¼" dice)
• 1 tablespoon minced garlic
• 8 ounces brown mushroom (½" thick slices)
• 2 tablespoons all-purpose flour
• 1 ½ cups unsalted beef broth (or stock)
• 1 tablespoon Dijon mustard
• ½ cup sour cream
• 2 teaspoons chopped parsley