With long knife, cut horizontally through long side of tenderloin, halfway up side of meat, stopping approximately ½ inch from other side.
Open beef as if opening a book.
Cover with plastic wrap or waxed paper.
Pound beef with flat side of meat mallet or rolling pin until uniformly ¼ inch thick.
In 10-inch skillet, melt 1 tablespoon butter over medium-high heat.
Cook mushrooms in butter, stirring occasionally, until tender and liquid has evaporated.
Cool 5 minutes.
Add bread crumbs, cheese and parsley; toss to combine.
Sprinkle bread crumb mixture over beef to within 1 inch of edges.
Tightly roll up, beginning with long side.
Turn small end of beef under about 6 inches so it cooks evenly.
Tie with kitchen string at 1½-inch intervals.
Place beef, seam side down, on rack in shallow roasting pan.
Brush with oil; sprinkle with salt.
Insert ovenproof meat thermometer so tip is in center of thickest part of beef.
Bake uncovered 30 to 40 minutes or until thermometer reads at least 140°F.
Cover loosely with foil; let stand about 15 minutes or until thermometer reads 145°F.
Meanwhile, in 1-quart saucepan, heat sauce ingredients to boiling, stirring occasionally; reduce heat to low.
Simmer uncovered 35 to 40 minutes, stirring occasionally, until sauce is slightly reduced and syrupy.
Remove string from beef before slicing.
Serve with sauce.
Notes / Tips / Wine Advice:
Make-Ahead Magic
Take the stress out of last-minute prep by making the sauce up to 24 hours in advance. Cover and refrigerate in a microwavable serving bowl until serving time. When ready to serve, microwave on High 30 seconds to 1 minute, stirring occasionally, until hot. (Sauce may have thickened. To thin sauce, stir in an additional 1 to 2 tablespoons of wine or beef broth if desired.)
Festive Touch
For an easy and seasonal garnish, arrange fresh sprigs of rosemary on the platter with the meat.
