Step 1: In a small bowl, sprinkle the gelatin over the cold water and let it bloom for 5 minutes. Melt it gently in the microwave for 10 seconds until clear, then set aside to cool slightly.
Step 2: In a large mixing bowl, whisk together the pumpkin puree, granulated sugar, cinnamon, ginger, nutmeg, cloves, and vanilla extract until the spiced pumpkin mousse with candied pecans recipe base is completely smooth.
Step 3: In a separate chilled bowl, whip the heavy cream until stiff peaks form. Slowly drizzle the melted gelatin into the cream during the final seconds of whipping to stabilize the spiced pumpkin mousse with candied pecans recipe.
Step 4: Gently fold one-third of the whipped cream into the pumpkin mixture to lighten it. Fold in the remaining cream in two batches using a spatula, being careful not to deflate the mixture.
Step 5: Transfer the spiced pumpkin mousse with candied pecans recipe into individual serving glasses and refrigerate for at least 3 hours.
Step 6: To make the candied pecans, melt butter in a small skillet over medium heat. Add the pecans and brown sugar, stirring constantly for 3-5 minutes until the sugar has caramelized and coated the nuts. Spread on parchment paper to cool.
Step 7: Just before serving the spiced pumpkin mousse with candied pecans recipe, top each glass with a generous handful of the candied pecans.