Take the pork tenderloin from the refrigerator, season with salt and black pepper, and lightly sear in a large sauté pan till a light brown crust forms. Set aside. For the herbed salt crust, combine the flour, chopped rosemary, chopped thyme and 1 ½ pounds of salt in a large mixing bowl. Gradually add the egg whites, mixing with your hands, until the mixture forms a soft but not sticky dough. Flour your hands and turn the dough out onto a work surface and knead until smooth. Wrap in plastic. Let stand at least 2 hours at room temperature or up to 1 day, refrigerated.
Make the egg wash. Take the 2 eggs and 1 tablespoon of water and whisk until incorporated evenly, about 10 seconds. After the dough has rested, flour a large work surface. Pull off 1/3 of the dough and keep the rest covered. Flour the rolling pin and roll the dough into a 14-by-6 inch rectangle. Line the baking sheet with parchment paper and put the dough on top of it. Set aside. Roll the remaining dough into a 20-by-10 inch rectangle. Take the seared tenderloin and place it in the middle of the smaller rectangle of dough. Place the remaining sprigs of thyme and rosemary, and the sliced garlic and place on top of the tenderloin. Take the egg wash and brush the area of dough not covered by the tenderloin. Take the larger piece of dough and gently place it on top of the tenderloin. Press the top piece of dough around the tenderloin to seal it well. Trim the excess dough from the top rectangle, 2-inches from the base of the tenderloin; leave the bottom piece of dough as is. Brush the top of the crust with more egg wash and sprinkle with the coarse sea salt. Set aside in the refrigerator till ready to bake.
Preheat oven to 450 degrees F. Bake until a long metal skewer inserted through the center of the tenderloin for 5 seconds, feels hot, about 25 minutes. Remove from oven and let rest for 15 minutes. To serve, take a paring knife and make a shallow incision near the base of the tenderloin, being careful not to cut into the tenderloin, and trim all around the tenderloin. Remove the "top of the salt crust" and place the tenderloin on a cutting board. Slice the tenderloin into the desired thickness and serve.