Preheat oven to 350°F. Butter a 9- x 13-inch baking dish.
In a medium bowl, combine crumbs, butter and 2 tablespoons brown sugar, and then press firmly into prepared dish to cover the bottom and part way up the sides evenly. Bake for 10 minutes; set aside to let cool.
Beat together pumpkin, cream cheese, 3/4 cup brown sugar, vanilla, cinnamon and cloves with an electric mixer until smooth and creamy, 3 to 4 minutes. Pour evenly over cooled crust; set aside.
In a large, clean bowl, beat cream and remaining 2 tablespoons brown sugar until stiff peaks form. Drop onto pumpkin mixture in dollops, then using a spatula, swirl the two together. Smooth the top, scatter pecans over the top (if using), cover and chill for 8 hours, or overnight.
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