In a cup, dissolve cornstarch in 1 tsp. water. In a medium saucepan over medium-low heat, combine pumpkin, 1/2 cup cream, brown sugar, maple syrup, spices and salt. Cook, whisking constantly, for 5 minutes, until sugar dissolves. Stir in cornstarch mixture, bring just to a boil, reduce heat to low, and cook, whisking, for 2 minutes. Strain through a fine-mesh sieve into a large bowl and cool completely.
In a chilled bowl using chilled beaters, whip remaining 1 cup cream and vanilla extract until firm peaks form. Fold 1/3 of whipped cream into pumpkin mixture to lighten, then fold in remaining cream until no streaks remain. Divide half of mousse among serving bowls or glasses and sprinkle with half of cookie crumbs. Repeat with remaining mousse and crumbs. Cover and chill 4 hours or up to 1 day.