Start by making the cake. Preheat the oven to 350℉. Cover the bottom of a 12x17 rimmed baking sheet with parchment paper and coat lightly with cooking spray. Using a mixer fitted with the whisk attachment, beat the egg yolks in a large bowl on medium-high speed for about 2 minutes, until thick and frothy. Add the brown sugar and mix on medium speed for 1 minute longer. In a separate bowl, stir together the flour, baking powder, baking soda, salt, and spices. Add the dry ingredients to the egg yolk mixture one-third at a time, beating on medium speed between each addition until incorporated. Add the pumpkin and mix on low speed until combined. Pour the egg whites into a clean, large bowl. Using a mixer fitted with the whisk attachment, whip them on high speed about 1-2 minutes, until soft peaks form. Add the white sugar, 1 tablespoon at a time, beating on high speed after each addition, until incorporated. Fold the egg whites gently into the batter. Spoon the batter evenly into the prepared pan and smooth carefully; it will not even out as the cake bakes. Bake for 15-20 minutes, until the cake is golden brown and springs back when touched lightly. Let the cake cool for 5 minutes. Turn out cake onto clean tea towel. Gently peel off the parchment paper. Gently roll the cake with the towel into a nice roll shape (rolling the 12 in side, not the 17 in side). Let cake cool in this position while you make the filling. Using a mixer fitted with a paddle attachment, beat the cream cheese on medium speed until creamy. Add the mascarpone and beat until incorporated. Add the powdered sugar, vanilla, allspice, cinnamon, nutmeg, and salt; beat on medium-high speed about 1 minutes, until combined. Transfer this mixture to another large bowl. Change mixer to the whisk attachment, and add the cream. Mix on high for 1-2 minutes until soft peaks form. Gently fold together the cream cheese mixture and the cream.
Unroll the towel and cake, and top the cake with the filling. Using a frosting knife or a simple bread knife, spread the filling evenly around the cake, leaving the 2 inches of cake bare that will be the last to be rolled up. Begin the roll the cake back up, working gently and slowly as to not break the cake. When the cake is completely rolled up, set it on a rectangular serving plate or wrap it well and refrigerate it for up to 2 days.
Lastly, to make the caramel sauce, heat the sugar over medium heat in a heavy-duty saucepan until it is completely melted and turns amber in color, about 5 minutes. Decrease the heat to low and immediately add the butter all at once, stirring to combine (it will bubble up). Add the cream, a couple of tablespoons at a time, stirring to combine between each addition. Adding the cream slowly keeps the caramel from clumping. Continue stirring until the caramel sauce is melted and smooth. Remove from the heat and stir in the rum (*optional*). You'll have about 1 ½ cups caramel sauce. Caramel can be stored in a covered glass container in the fridge for up to 3 weeks (it's also amazing addition to your morning coffee).
To serve, cut the roll with a serrated knife. Serve with a pitcher of warm caramel sauce and a bowl of the remaining whipped cream and let guests serve themselves.
