Preheat oven to 400 degrees. Line a large baking sheet with parchment paper; set aside. In a medium saucepan combine water, butter, sugar, and salt. Bring to boiling over medium hear. Add flour all at once, stirring vigorously with a wooden spoon. Cook and stir until the mixture forms a ball and pulls away from the sides of the pan. Remove from heat, cool for 10 minutes. Add eggs one at a time, blending well with wooden spoon after each egg. Drop 8 heaping Tbs. of dough 2" apart. Bake for 30 to 35 minutes until golden and firm. Transfer cream puffs to a wire rack and cool. Using a serrated knife, cut each cream puff in half horizontally; remove soft dough from inside. Fill cream puffs with Pumpkin Mousse. Replace tops. Spoon some of the warm Maple-Caramel sauce onto dessert plates; sprinkle with pecans. Place a cream puff on each plate, drizzle each with remaining sauce and sprinkle with remaining pecans.
Pumpkin Mousse: In a chilled large mixing bowl beat 1 cup whipping cream, 3 Tbs. sugar, and 1 tsp. pumpkin pie spice with the chilled beaters of electric mixer, on medium speed until soft peaks form. Fold in 1 cup canned pumpkin. Cover and chill for up to 4 hours.
Maple-Caramel Sauce: In a small heavy saucepan stir together 1/2 cup packed brown sugar and 1 Tbs. cornstarch. Stir in 1/3 cup half & half or light cream, 1/4 cup water, 2 Tbs. pure maple syrup, and 1 Tbs. butter. cook and stir over medium heat until slightly thickened and bubbly (mixture may appear curdled before it bubbles.) Cook and stir for 2 minutes more. Remove from hear, stir in 1/3 tsp. vanilla. Serve warm.