3/4 pound unsalted butter (3 sticks) softened and cut into pieces
1 1/4 cup pureed blackberries
Instructions
For the cake:
Preheat the oven to 350 degrees. Preheat oven to 350 degrees, grease and cover the bottom of 3 9 inch cake pans with wax paper and prepare ingredients.
Whisk the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment.
In another bowl, combine the buttermilk, oil, eggs, vanilla, almond, and bourbon. With the mixer on low speed, slowly add the wet ingredients to the dry.
Next, add in the coffee and mix to combine.
Pour the mixture evenly into the prepared cake pans and bake for 20-30 minutes.
For the buttercream:
Put eggs whites and sugar in a heatproof bowl set over a pot of simmering water. Whisk until sugar is completely dissolved and mixture reaches 160 degrees.
Remove bowl from heat and attach the bowl to a mixer, whisk on medium-high speed for 5 minutes or until very stiff peaks form. Lower speed to medium and start adding butter one piece at a time until are all combined. Whisk until stiff peaks form again if you lost definition when adding the butter.
Switch to the paddle attachment and on low speed slowly add a little bit of the blackberries, keep mixing and adding blackberries until all are combined. Whisk on medium speed to firm up the mixture.
Notes
For successful swiss meringue buttercream with fresh fruit, make sure your heat-proof bowl is completely dry to start.
If you don't have a candy thermometer, keep testing the egg and sugar mixture until all the sugar granules have dissolved.
Whisk until you have very stiff peaks; this is the step when you build up a lot of the structure. Once the berries get added, the buttercream will turn to soup if it's not thoroughly whipped.
Add the butter and thoroughly whisk until it reaches stiff peaks again.
Add the blackberry puree. If it starts to et soupy, chill it in the refrigerator for 30 min, and it should stiffen up.