Heat oven to 425f. Place mushrooms and shallot into food processor; pulse on and off about 10 times until finely chopped. Do not over process. Heat remaining 1/2 teaspoon oil in same skillet over medium-high heat until hot. Add mushrooms and shallot; cook 4 to 6 minutes until tender and all liquid is evaporated, stirring often. Add wine; cook 2 to 3 minutes until all liquid is evaporated. Stir in mustard, thyme, remaining 1/4 teaspoon pepper. Cook 2 to 3 minutes. Remove from skillet to medium bowl; cool. and place in oven. Unfold pastry dough on lightly floured cutting board. Roll pastry out to 12 by 9-inch rectangle; lay dough with shortest edge toward you. Spread mushroom mixture onto pastry dough, leaving 1/2-inch border around edge of dough. Place roast in center of mushrooms. Fold pastry dough neatly around roast, stretching dough if necessary. Cut off excess pastry dough; press to seal overlapping edges. Remove baking sheet from oven and dust lightly with flour. Place pastry- wrapped roast, seam-side down, on baking sheet. Cut 4 (2-inch) vents in top of pastry.
