Remove the bavette steak from the refrigerator and let it rest at room temperature for about 30 minutes. Season both sides generously with salt and pepper.
In a large skillet, heat the olive oil over medium-high heat. Once hot, add the seasoned steak to the skillet. Sear for about 4-5 minutes on each side for medium-rare, or until desired doneness is reached. Transfer the steak to a cutting board and let it rest while you prepare the sauce.
In the same skillet, reduce the heat to medium and add the minced garlic. Sauté for about 1 minute until fragrant but not browned.
Carefully pour in the beef stock and scrape any browned bits from the bottom of the skillet with a wooden spoon. Bring the mixture to a simmer and cook for about 3-4 minutes until it slightly thickens.
Stir in the Dijon mustard and mix well. Remove the skillet from heat and add the butter, swirling it into the sauce until melted and combined.
Thinly slice the bavette steak against the grain. Arrange the slices on a serving platter and generously drizzle with the garlic pan sauce.
Finish with a sprinkle of chopped fresh parsley for color and added freshness.
Notes
Let the steak rest before slicing for better juiciness.