To prepare vanilla cream, combine first 4 ingredients in a small saucepan, stirring with a whisk until well blended. Gradually add 1 cup milk and half-and-half, stirring with a whisk. Cook over medium heat until mixture comes to a boil, stirring constantly. Reduce heat to low; cook 1 minute, stirring constantly. Remove from heat; stir in vanilla. Pour into a bowl. Press plastic wrap onto surface of vanilla cream; chill.
Preheat oven to 375°.
To prepare shells, cut out 6 (12 x 6-inch) pieces of aluminum foil. Using index fingers as a guide, loosely roll up each foil piece jelly-roll fashion to form a cylinder with a 1-inch opening. Lightly coat outside of each cylinder with cooking spray.
Place 1 phyllo sheet on a large cutting board or work surface (cover the remaining dough to prevent drying); lightly coat with cooking spray. Sprinkle evenly with 1 tablespoon granulated sugar. Repeat layers once. Cut phyllo stack lengthwise into 3 equal strips. Repeat procedure with remaining phyllo, cooking spray, and granulated sugar. Place a foil cylinder at the bottom of 1 phyllo strip, and roll up phyllo jelly-roll fashion around cylinder. Lightly coat with cooking spray. Place on a parchment-lined baking sheet. Repeat the procedure with remaining foil cylinders, phyllo strips, and cooking spray. Bake at 375° for 10 minutes or until lightly browned. Cool completely on a wire rack. Carefully remove foil cylinders from phyllo shells by twisting ends of foil in opposite directions and gently pulling foil from shells.
Spoon vanilla cream into a zip-top plastic bag. Seal bag; snip off 1/2 inch of 1 bottom corner of bag. Pipe vanilla cream evenly into cooled phyllo shells.
Place chocolate chips and 1 1/2 teaspoons milk in another zip-top plastic bag. (Do not seal bag.) Microwave at HIGH 45 seconds or until chocolate melts; lightly knead bag until mixture is smooth. Snip off 1/4 inch of 1 bottom corner of bag. Drizzle chocolate mixture evenly over stuffed shells. Sprinkle with the powdered sugar. Serve immediately.