Preheat the oven to 375 degrees F (190 degrees C) and get out a jelly roll pan. Lightly spray it with cooking spray, which helps the parchment paper stay put. Then line it with parchment paper with enough over hang to be able to lift the cake out of the pan. Lightly spray the parchment paper too.
Then whisk the All-Purpose Flour (3/4 cup), Baking Powder (1/2 teaspoon), Baking Soda (1/2 teaspoon), Pumpkin Pie Spice (2 teaspoon), Ground Mace (1/2 teaspoon) and Salt (1 pinch) together in a bowl.
In another large mixing bowl, whisk the Dark Brown Sugar (1 cup), Canned Pumpkin Purée (2/3 cup), Pumpkin Spice Extract (1 teaspoon), and Egg (3) together for a minute or so to really get some air into it. Then use a spatula to gently fold in the dry ingredients just until they disappear in.
Spread the batter evenly in the prepared jelly roll pan and bake it for 13-15 minutes. It should be springy when it's done. It will obviously be really hot, so use oven mitts to lift the cake out of the pan and gently roll up the cake from the short side to the other short side tightly while it is still in the parchment paper. Set it seam side down on a cooling rack to cool completely.
While it cools, make the easy filling. Combine the Butter (1/2 cup) and Mascarpone Cheese (8 ounce) in a bowl and beat them together until fluffy with a hand mixer. Then beat in the Pumpkin Pie Spice (1/2 teaspoon).
Finally, slowly beat in the Powdered Confectioners Sugar (3 cup) until you have a luscious frosting. Cover it and set it in the refrigerator for 30 minutes to let it firm back up a little.
When the cake is cool and the frosting has firmed back up, gently unroll the cake and spread the frosting all over it, leaving a border for it to slightly squish out when you roll it back up. Roll it back up and remove the parchment paper as you do it.
Wrap the cake in plastic and refrigerate it to completely set for at least an hour or two.
When it's time for dessert, dust the top generously with more powdered sugar, Slice and serve! Enjoy!!