Link to original recipe: https://www.myrecipes.com/recipe/stuffed-beef-tenderloin-with-burgundy-mushroom-sauce
Ingredients:
for the beef-- 2 (10-oz.) pkg. frozen chopped spinach, thawed
3 T. unsalted butter
2 medium leeks, thinly sliced
1 garlic cloved, minced
3 T. all-purpose flour
1 c. heavy cream
1 oz. Parmesan-Reggiano, grated
2 tsp. fresh lemon juice
1/4 tsp. grated whole nutmeg
2 tsp. kosher salt, divided
1 tsp. black pepper, divided
4 lb beef tenderloin section, trimmed
for the sauce--
2 T. unsalted butter, divided
1 T. olive oil
16 oz. cremini mushrooms, quartered
1 medium shallot, minced
1/2 c. dry red wine
1 c. beef broth
1 T. Dijon mustard (I think we used Grey Poupon-style one)
1/2 tsp. fresh rosemary
1/2 tsp. kosher salt
1/4 tsp. black pepper
Directions:
1. Drain spinach well, pressing between paper towels to remove excess moisture.
2. In a medium saucepan over medium heat, melt the butter. Add leeks and garlic and cook, stirring occasionally, until softened (around 3-4 min).
3. Sprinkle flour atop the mixture and stir, cooking for another 3 min.
4. Whisk in cream until smooth. Stir in spinach and cook, stirring occasionally, until mixture is thickened (around 5 min.)
5. Add cheese, lemon juice, nutmeg, 1 tsp. of the salt, and 1/2 tsp. of the pepper, stirring to combine. Remove from heat and let mixture cool for 10 min. Heat oven to 350°F.
6. Meanwhile, butterfly the beef and open it like a book, spreading flat. Place between 2 sheets of plastic wrap and pound to 1/2" thickness all over using a meat mallet, making around a 13" square (we had to piece the meat together a little to do this).
7. Remove plastic wrap and spread the cooled mixture evenly over the beef, leaving a 1/2" border around edges. Roll up beef and tie with kitchen twine.
8. Brush all over with olive oil, then sprinkle with remaining salt and pepper. Place beef on a wire rack set over a rimmed baking pan. Transfer to oven and bake for 30 min.
9. Increase heat to 450°F and bake for additional 20 min, or until meat thermometer registers 125°F inserted in center. Let stand 30 min. before slicing.
10. While beef rests, prepare the sauce. In a large skillet over medium-high heat, melt 1 T. of the butter together in skillet with olive oil (swirl to combine), then add mushrooms. Cook, stirring a couple of times, until lightly browned (around 5-6 min.)
11. Add shallot and cook, stirring constantly, 1-2 min. Carefully add wine to skillet and stir in, cooking 2 additional minutes.
12. Stir in broth and reduce heat to medium. Let simmer for 5 minutes.
13. Mix in the mustard, rosemary, salt, and pepper. Cook for 1 minute. Remove from heat and stir in the remaining 1 T. butter until combined. Serve sauce with beef and enjoy!
