FOR 2 servings: Heat 1 Tbsp. oil in sauté pan on medium heat. Add 1 cup mushrooms; sauté 4 min. Remove from heat. Stir in 1/4 cup champagne. Return to heat; cook 3 min. or until mushrooms are almost dry. Add to 2 oz. cream cheese in small bowl; mix well. Spoon into pastry bag. (Do not fit pastry bag with tip.)
PLACE 1 piece of pork on cutting board. Starting at one end, use paring knife to cut lengthwise tunnel in center of pork, being careful to not cut through sides or all the way to other end. Insert pastry bag into the pork and fill wth cream cheese mixture. Season with 1/4 tsp. salt.
HEAT 1 Tbsp. of the remaining oil in sauté pan on medium heat. Add pork; cook 5 min. on each side, or until done (145ºF). Remove from pan; let stand 5 min. before cutting into 4 slices to serve.
FOR each serving: Mound 1/2 cup "Creamed" Cabbage Gratin onto center of serving plate; top with 2 tenderloin slices. Sprinkle with 1/4 tsp. chives.