Preheat oven to 350F and grease and flour three 6" cake rounds, line with parchment.
In a medium bowl, whisk flour, baking powder, salt, and spices. Set aside.
Using a stand mixer fitted with the paddle attachment, beat butter until smooth. Add sugars and beat on med-high until pale and fluffy (2-3mins).
Reduce speed and add eggs one at a time, fully incorporating after each addition. Add molasses and vanilla and mix until incorporated.
Alternate adding flour mixture and buttermilk, beginning and ending with flour (3 additions of flour and 2 of milk). Fully incorporating after each addition. Do not overmix.
Spread batter evenly into prepared pans. Smooth the tops with a spatula.
Bake for approx. 30-35 mins or until a toothpick inserted into the center comes out mostly clean.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack to cool completely.
Espresso Swiss Meringue Buttercream:
Place egg whites and sugar into the bowl of a stand mixer, whisk until combined.*
Place bowl over a pot with 1-2" of simmering water and whisk constantly until the mixture is hot and no longer grainy to the touch or reads 160F on a candy thermometer (about 3mins).
Place bowl on your stand mixer and whip on med-high until the meringue is stiff and cooled (the bowl is no longer warm to the touch (approx. 5-10mins)).
Switch to paddle attachment. Slowly add cubed butter and mix until smooth.**
Add vanilla and whip until smooth. Remove 3 cups of buttercream, set aside for white fault line frosting.
Add espresso to remaining buttercream and whip until smooth.***
Assembly:
Place one layer of cake on a cake stand or serving plate. Top with 2/3 cup of frosting. Repeat with next layer.
Place the final layer on top and do a think crumb coat on the cake. Chill for 30mins.
Frost and smooth the outside of the cake, generously frosting the sides specifically. Smooth with an icing smoother. Use a cake comb on the sides of the cake. Repeat, scraping off more frosting each time, until smooth. Chill for 30mins.
Once the cake is chilled, use a straight spatula to add the white buttercream around the base of the cake. Allow some of the buttercream to go higher up the cake to create depth. Smooth the white frosting with an icing scraper. Patch as needed and repeat.
Do dollops of the white frosting on top using a Wilton 4B piping tip. Sprinkle small and large white nonpareils on top as well as some chocolate crispearls and candied ginger if desired. Place coffee beans along the bottom.
Notes
* Ensure there is NO trace of egg yolks in your whites and that your mixer bowl and whisk is completely grease free or your meringue won't stiffen.** The buttercream may look like it's curdled at some point. Keep mixing until it is completely smooth.*** If your instant espresso is not a superfine powder, I recommend dissolving it first in 1-2 tsp hot water and cooling before adding to the frosting.