The 2 hour chilling time is not included in the prep time!! To prepare ahead, you can get the caramelized pear cannoli made, and store in the refrigerator up to 2 days ahead of time. The praline sauce can be made up to 3 days ahead and stored in the refrigerator, covered. To heat, place over low heat until warm, stirring often. If you can't find cannoli shells, you can buy pizzelles and layer the peach mixture between them before topping with the praline sauce and toasted pecans.
Preheat oven to 400°. Toss together the first 3 ingredients. Spread in a single layer on a parchment paoer lined 15 x 10 inch jelly-roll pan. Bake 30 to 35 minutes or until lightly browned and tender. Reduce oven temperature to 350°. Remove pears from oven and let cool 20 minutes.
Meanwhile, bake pecans at 350° in a single layer in a shallow pan for 6 to 8 minutes or until toasted and fragrant, stirring halfway through.
Stir together the pears, mascarpone, and lemon zest. Beat the cream and powdered sugar at high speed with an electric mixer until soft peaks form. Fold the whipped cream into the pear mixture.
Spoon the pear mixture into a zip-top plastic freezer bag; snip 1 corner of the bag to make a 1-inch hole. Pipe pear mixture into the cannoli shells. Place in a 13 x 9 x 2 inch pan. Cover and chill 2 hours before serving. Serve cannoli with warm Praline Sauce, and sprinkle with toasted pecans.
Praline Sauce: Bring the first 3 ingredients to a boil in a small sauce pan over medium heat, stirring constantly. Cook, stirring constantly for 1 minute. Remove from heat, and stir in vanilla. Cool slightly, about 10 minutes. Serve warm.