A.1.-Béarnaise Chateaubriand

Ingredients

• 0.3 tsp pepper black
• 0.8 cup butter divided (1-)
• 1  egg yolk 
• 2 Tbsp parsley fresh finely chopped
• 2 tsp tarragon or dried fresh chopped
• 0.5 cup a.1. original sauce divided
• 2.5 lb new potatoes peeled
• 2 lb beef tenderloin roast 
• 0.5 tsp salt 
• 2 Tbsp shallots chopped

Equipment

• frying pan
• sauce pan
• oven
• whisk
• double boiler
• baking pan

Directions

1. Preheat oven to 425F.
2. Place roast in baking pan; brush with 2 Tbsp. of the steak sauce.
3. Bake 35 to 40 minutes or until internal temperature reaches 140F for medium-rare or 155F for medium doneness, brushing with 2 Tbsp. of the remaining steak sauce after 20 minutes.
4. Let stand 15 minutes (internal temperature will rise 10F during standing).
5. Place potatoes in large saucepan.
6. Add enough water to cover. Bring to boil on medium-high heat. Reduce heat to medium-low; simmer 10 to 12 minutes or until potatoes are tender.
7. Drain potatoes, leaving potatoes in pan.
8. Cut 1/4 cup of the butter into pieces; add to potatoes along with the parsley. Toss tightly until potatoes are evenly coated. Season with the salt and pepper. Cover to keep warm.
9. Fill bottom of double boiler with a few inches of water. Bring to boil on medium-high heat. Meanwhile, mix remaining 1/4 cup steak sauce and shallots in top of double boiler; place directly on burner (not over the bottom part of the double boiler filled with water) and cook 3 minutes or until thickened, stirring frequently.
10. Add 2 Tbsp. of the remaining butter; stir until melted.
11. Remove from heat.
12. Add egg yolk and tarragon; stir with wire whisk until well blended.
13. Place over bottom of double boiler filled with simmering water; cook and stir until thickened.
14. Add the remaining 6 Tbsp. butter, 2 Tbsp. at a time, stirring with wire whisk after each addition until butter is completely melted.
15. Remove from heat; cover to keep warm.
16. Cut meat into slices. Top with the sauce.
17. Serve with the potatoes.