Preheat the oven to 425ºF. Line a 17X12 jelly roll pan with parchment; butter and flour the parchment.

In a large bowl, combine the cocoa powder, flour, salt, and baking powder. Set aside.

Combine eggs and sugar in a (stand-)mixer bowl. Set this over a pan of simmering water (make sure the bowl doesn't touch the water). Beat by hand for a couple of minutes or until the eggs are warm-hot to the touch.

Remove from the heat and beat at high speed for 3-5 minutes, until the mixture is thick, pale yellow, airy, falls in ribbons and holds its shape for about 5 seconds.

Gently mix in the melted butter. Fold in the dry ingredients, quickly.

Spread the batter onto your buttered parchment and bake for 5–6 minutes, or until the surface springs back when touched.

Once the sponge is out of the oven, use a sharp knife to release the sides. Then dust another baking sheet with cocoa, and--very quickly--invert, peel off parchment, return parchment to the original baking sheet, and re-invert the cake onto the original tray. Now let it cool completely.

Choose glasses or other ramekins to set the mousse. Use these to invert onto the chocolate sponge and cut out rounds. Insert into the glasses. If there are any crumbs, torn pieces, or left-overs, mourn not! Use these to create a second layer in a single cup! Set aside until you make the mousse.

In a small bowl sprinkle the unflavored gelatin over 1/4 cup Drambuie to soften for 5 minutes. Set the mixture over a bain marie (double boiler) and stir until the gelatin is dissolved.

In a large, clean bowl beat the 4 egg whites until frothy, then add 1/4 teaspoon cream of tartar or salt, and continue beating. Slowly add in the remaining 1/3 cup sugar, a little at a time, beating until it holds stiff peaks.

Fold this meringue into the partially cooled pumpkin mixture, working quickly.

Layer the mousse onto the prepared glasses with chocolate sponge. Add any left-over sponge cake, and finish with more mousse. (Or just create a single layer of cake and mousse).

Refrigerate until set and well-chilled, about 4-6 hours.

Whip together the chilled heavy cream and creme fraiche (or use just heavy cream) until stiff peaks form. Top the set mousses with generous spoonfuls of this mixture, and dust over top with cinnamon to serve.