Ingredients:

  • 1 lb (450g) Beef Tenderloin (Chateaubriand cut, trimmed)
  • 1 Tbsp Olive Oil (for beef)
  • Coarse Sea Salt (to taste)
  • Freshly Cracked Black Pepper (to taste)
  • 1 loaf Baguette (sliced diagonally into 1/2-inch pieces)
  • 2 Tbsp Olive Oil (for brushing bread)
  • 1/4 cup Dry White Wine (e.g., Sauvignon Blanc)
  • 1 Tbsp White Wine Vinegar
  • 1 Tbsp Shallot, finely minced
  • 1 Tbsp Fresh Tarragon leaves, chopped (plus extra for garnish)
  • 3 Large Egg Yolks (room temperature)
  • 1 stick (8 Tbsp / 113g) Unsalted Butter, chilled & cubed
  • 1 tsp Fresh Lemon Juice
  • Pinch of Cayenne Pepper

Instructions:

  1. Preheat the grill or grill pan to medium-high heat (about 400°F / 200°C). Toss the tenderloin lightly in olive oil, salt, and pepper.
  2. Grill the tenderloin 3-4 minutes per side for medium-rare (internal temp 130–135°F / 54–57°C). Remove steak, tent loosely with foil, and rest for 10 minutes.
  3. While the steak rests, slice the baguette diagonally into 1/2-inch thick pieces. Brush lightly with olive oil and toast on the grill or under the broiler until light golden and crisp. Set aside.
  4. Make the Barnaise Reduction: Combine white wine, vinegar, minced shallot, and 1/2 Tbsp of the chopped tarragon in a small saucepan. Simmer over medium heat until reduced to about 1–2 tablespoons of liquid.
  5. Strain the reduction into a medium stainless steel bowl, discarding solids. Let cool slightly.
  6. Create a double boiler (bain-marie) with the bowl over gently simmering water (ensure water does not touch the bowl bottom). Whisk the three egg yolks vigorously into the reduction until the mixture lightens in colour and thickens slightly.
  7. Slowly begin whisking in the cold cubed butter, one piece at a time, ensuring each piece is almost fully incorporated before adding the next. Keep whisking constantly until all butter is incorporated and the sauce is thick enough to coat the back of a spoon.
  8. Remove the bowl from heat. Whisk in the lemon juice and cayenne pepper. Keep the Barnaise warm, but do not allow it to get hot.
  9. Slice the rested tenderloin thinly against the grain (about 1/4-inch slices).
  10. Assemble: Top each crostini generously with 1-2 slices of beef, drizzle with Barnaise sauce, and garnish with a tiny sprig of fresh tarragon. Serve immediately.