Pumpkin Mousse Trifle

Heat oven to 325 °F. Coat a baking sheet with cooking spray. Spread pumpkin seeds evenly on sheet; bake until golden, stirring once, about 25 minutes. In a bowl, mix pumpkin, cinnamon, nutmeg and cloves until smooth. In a second bowl, whip egg whites with an electric mixer until soft peaks form; add 1/2 cup sugar and whip until stiff peaks of meringue form. Gently fold pumpkin mixture into meringue until just combined. In a third bowl, combine sour cream and remaining 1 tablespoon sugar. In a food processor, pulse cookies into fine crumbs. In each of four 5-ounce glasses, divide and layer half of shortbread crumbs and half of pumpkin mousse; repeat layers. Top each with 1 tablespoon sweetened sour cream and sprinkle with pumpkin seeds; serve immediately.