In a small bowl, combine the flour, pecans, butter and sugar. Press into a greased 13-in x 9-in x 2-in baking dish. Bake at 350 degrees for 18-20 minutes or until golden brown. Cool on a wire rack. In a large saucepan, combine brown sugar and cornstarch. Stir in rhubarb until combined. Bring to a boil over medium heat, stirring often. Reduce heat; cook and stir for 4-5 minutes or until thickened. Remove from heat; cool. Stir in strawberries. In a small mixing bowl, beat cream cheese and powdered sugar until smooth. Fold in 1 cup whipped cream. Spread over crust; top with rhubarb mixture. Spread with remaining whipped cream. Refrigerate for 3-4 hours before serving. Garnish with additional brown sugar if desired.