Preheat oven to 350°F. Grease and line a jelly roll pan (preferable) or a half sheet baking pan with parchment paper and set aside.
In a standing mixer fitted with a whisk attachment, beat the egg whites over high speed until soft peaks form. Turn mixer to low speed and slowly add in granulated sugar. Turn mixer back to high speed and continue to whip until stiff peaks form. Remove from mixer and set aside.
Clean your standing mixer bowl and place back on stand. Add in the egg yolks. Still using the whisk attachment, beat egg yolks until they begin to foam. Add in molasses and vanilla extract and continue to beat until mixture becomes a shade lighter in color, about 3 minutes. Remove bowl from standing mixer and set aside.
In a small bowl, sift together flour, baking powder, cinnamon, ginger, nutmeg, cloves, and salt. Fold your flour mixture into your yolk mixture. The batter will be thick, but this will change once you add in your egg whites.
Using a spatula, gently fold your egg whites into your flour/yolk mixture until fully incorporated. Spread batter into prepared pan, using the spatula to smooth batter to the edges. Bake for 15-17 minutes, until the cake is cooked through. Cool for 5 minutes before inverting cake onto a kitchen towel dusted with confectioner's sugar (and to note: I left my parchment paper on the underside of the cake to prevent it from sticking to the towel).
Roll cake into a tight spiral, starting from the short side. Place in fridge to cool completely.
make your filling & frosting
In a standing mixer fitted with a whisk attachment, cream your heavy cream and vanilla extract until stiff peaks form. Unroll cake (& carefully remove parchment paper if you kept it on) and spread the whipped cream evenly over the cake. Roll up cake.
Cut cake about 4 inches from the edge on a diagonal to create the second part of your log. Place larger roll seam side down onto a platter. Place the smaller roll on the side of the first roll, with the diagonal side of the smaller roll touching the larger roll.
In a standing mixer fitted with a paddle attachment, cream butter for 2 minutes, then add in melted and cooled white chocolate. Combine, then add in powdered sugar, vanilla extract, and salt, creaming for about 30 seconds.
Spread white chocolate buttercream over the cake, leaving the edges of the logs bare. Use a fork to make soft waves throughout the buttercream. Sprinkle with cinnamon sugar. Serve!