Set an oven rack in the middle of the oven. Preheat oven to 450°F. Melt the butter and set aside. Coat an 11- x 17-inch rimmed baking sheet with cooking spray. Line the pan with parchment paper. Now lightly coat the paper lightly with cooking spray.
Place the 1 Tbsp. cocoa powder into a small, fine sieve. Now dust and coat, evenly as you can, the parchment paper on the baking sheet with that cocoa powder, gently taping the sieve to release it. Set pan aside.
Place the flour, ¼ cup cocoa powder and salt in a bowl, whisk to combine, and then set aside.
Combine eggs, egg yolks and sugar in the bowl of your stand mixture. Set the bottom 1/3 of the bowl into warm water and whisk lightly until the egg/sugar mixture is lukewarm.
Set the bowl on your stand mixture fitted with the whip attachment. Beat on medium-high until mixture is pale and thick, about 7 minutes. Beat in the melted butter.
Sprinkle the flour mixture over the egg mixture. Use a large spatula to gently and carefully fold the two mixtures together.
Spoon the batter into the prepared baking sheet and evenly spread into an even, thin layer. Bake cake until puffed and springy to the touch, about 6 minutes.
Cool cake 5 minutes, and then run a knife around sides of cake to loosen if stuck. Set a clean kitchen towel on a work surface. Quickly inverted the cake pan, releasing the cake onto to the towel. While the cake is still warm, gently roll into a log, incorporating the kitchen towel. Let the rolled cake cool completely in towel (This will established its rolled form and make easier to roll again with filling.)
For the filling
Place the cranberries and rum, brandy or apple juice in a small pot. Bring to a boil, and then remove from the heat and let cranberries steep 2 hours, until plump and softened. Set a fine sieve over a small bowl. Spoon the cranberries into the sieve to drain. Set drained cranberries in clean bowl. Reserve cranberry soaking liquid.
Whip the cream until soft peaks form. Mix in the icing sugar, vanilla and 2 Tbsp of the cranberry soaking liquid. Beat the cream until firm peaks form.
Carefully unroll the cake from the kitchen towel onto a work surface. Brush the top of the cake with the remaining cranberry soaking liquid. Spread the cake with the whipped cream mixture, leaving a 1/2-inch border all around. Disperse the mandarins orange pieces and cranberries on top of the whipped cream. Carefully, and tightly as you can, roll the cake up, sealing the filling inside.
Now very carefully transfer the roll to a long serving platter. Wrap and refrigerate until ready to serve; Swiss roll can be made several hours in advance of serving.
When ready to serve, unwrap and dust roll with cocoa powder, to taste. Slice and enjoy.