
1 (3-pound) center-cut beef tenderloin roast
1 tablespoon coarse kosher salt
1 tablespoon coarsely ground black pepper
1 large shallot, coarsely chopped
1 clove garlic, peeled
1 (8-ounce) package baby bella mushrooms
1 (4-ounce) package shiitake mushrooms with stems
1 tablespoon unsalted butter
1 tablespoon olive oil
¼ cup sherry vinegar
1 tablespoon fresh thyme leaves
½ teaspoon coarse kosher salt
½ teaspoon ground black pepper
2 tablespoons vegetable oil
2 tablespoons Dijon mustard, divided
10 to 12 thin slices prosciutto
1 (17.3-ounce) package frozen puff pastry (2 count)
All-purpose flour, for dusting
1 large egg, lightly beaten
1⁄8 teaspoon flaky sea salt, plus additional for garnish
Fresh thyme sprigs, for garnish
Fresh sage sprigs, for garnish