In a stand mixer fitted with the paddle attachment, combine 1 cup water with the salt, egg white, pepper, thyme, juniper, garlic, and parsley. Mix on medium speed until blended. On medium-low speed, mix in 2 cups of the flour, adding more as needed, until the dough is firm and feels slightly dry and stiff, like Play-Doh. Continue to mix for 2 minutes. The dough should be smooth and firm but not sticky; add more flour if necessary. Flatten the dough into a rectangle, wrap in plastic, and refrigerate for at least 2 hours and up to 6 hours.
An hour before you’re ready to roast, put the beef on the counter and let sit at room temperature.
Position a rack in the center of the oven and heat the oven to 350°F. Heat a large cast-iron skillet over medium-high heat. Add the oil and put the roast meat side down in the skillet; sear until deeply browned, about 5 minutes. Remove the roast from the pan and set it bone side down on a rack in a roasting pan.
On a lightly floured surface, roll the dough into a 1/4-inch-thick rectangle. Drape the dough over the meat, tucking it in on all sides. Roast until an instant-read thermometer in the middle of the roast registers 125°F for rare or 135°F for medium rare, 1-3/4 to 2-1/4 hours. Let rest for 20 minutes, then remove and discard the crust. (After removing the crust, the roast can rest for up to 30 minutes more.) Carve and serve with the Morel Sauce.