Heat oven to 350.
Grease a 15x10x1 baking or jelly roll pan or spray it with baking spray.
Line it with wax paper cut 1/2-in smaller than the pan.
Grease the paper or spray it with baking spray.
Sift flour, ground spices, salt, baking soda, and baking powder into a bowl or onto another sheet of wax paper.
In a mixer, beat egg yolks, optional orange juice, and vanilla until thick and yellow.
Add the molasses and butter and beat on high until thoroughly combined.
Add optional fresh grated ginger and orange zest.
Pour mixture into a clean bowl and set aside.
In a clean mixer, beat the egg whites on medium until soft peaks form.
Add the white sugar slowly and beat until stiff peaks form.
Fold the egg yolk mixture into the beaten egg white mixture with a spatula.
Quickly but gently, with a spatula, fold in the flour mixture.
Spread the batter as evenly as possible into the pan.
Bake 12-15 minutes until centre springs back when pressed lighly with a fingertip. [The cake may look a bit bubbly or even mountainous! No worries! It will flatten out with the folding, anyway!]
Immediately loosen the edges of the cake with a knife.
Invert warm cake onto a clean towel dusted generously with icing sugar.
Peel off waxed paper.
Gently roll wider length of cake jelly-roll-style in the towel.
Cool rolled and wrapped cake completely on wire rack. [You can store the cake like this for up to one day or re-roll the cake in wax paper, wrap wax-paper-rolled cake in foil and freeze for 2-3 weeks.]
Unroll your cake from the towel.
Using a pastry or baking-style brush, spread some of the soak (below, about 1/16 c) generously on the surface of the unrolled cake.
Spread the surface of the unrolled cake with the cream (below).
Gently re-roll the cake.
Brush the rolled cake with additional soak if desired.
Place the filled cake on a serving plate.
Cut 1-in or thicker slices from the ends of the cake roll to use as the knots/branches of the yule log.
Use the icing (below) to attach these knots/limbs to the cake roll where you see fit.
[Optional] Take a small bit of icing and “dirty ice” the exposed cake areas and iced edges with a thin layer of icing and let cake sit in the refrigerator for a while.
Ice the cake. You do not have to ice the open ends and open knots of the cake. This is a bit tricky, but can be done with a clean icing spreader.
If desired, use the tines of a fork or an icing spatula to make the log look like “tree bark.”
If desired, sprinkle certain areas of the log, such as the "knots" with cinnamon or nuts.
If desired, decorate with Make-Ahead Meringue Mushrooms, below.
If desired, decorate with candied or fresh orange peels or bits of candied ginger.
Chill until 20 minutes before serving.