1. In the bowl of an electric mixer fitted with the paddle attachment, combine 2 cups salt with 3 tablespoons thyme and 3 tablespoons rosemary. Add egg whites and 2/3 cup water; mix until thoroughly combined. A little at a time, add up to 2 cups flour, beating on medium speed, until mixture forms a firm, homogenous dough, 2 to 3 minutes. The dough should be firm but not too moist or sticky. If necessary, knead in additional flour or water. Form dough into a square; wrap in plastic. Let rest at room temperature at least 2 hours or up to 24 hours.
2. Preheat oven to 375 degrees F. Rinse tenderloin, and pat dry. Heat butter and olive oil in a large skillet set over medium-high heat. When skillet is hot, add beef. Sear well on all sides, about 1 1/2 minutes per side. Transfer tenderloin to a wire rack set over a baking pan to cool, 5 minutes.
3. On a lightly floured surface, roll out dough to an approximately 10-by-15-inch rectangle (rectangle should be large enough to completely encase tenderloin). Sprinkle remaining 1/4 cup thyme, 1/4 cup rosemary, the sage, bay leaves, parsley, and garlic over dough. Remove twine from tenderloin, and place it in the center of the dough. Roll dough around beef, completely encasing it. Press edges together to seal. Carefully transfer wrapped beef to a roasting pan. In a small bowl, mix egg yolks with 2 teaspoons water; brush entire surface of dough with egg wash. Sprinkle remaining 2 tablespoons salt over the top.
4. Place baking pan in center of oven. Roast until crust is light golden and an instant-read thermometer inserted into center registers 125 degrees F to 130 degrees F (for medium-rare), allowing 10 to 12 minutes per pound. Remove pan from oven; let rest at room temperature 1 hour.
5. When ready to serve, slice off the crust at one end, and remove beef; discard crust. Season beef with pepper, slice, and serve.

Yield: 6 servings