Preheat the oven to 350°F and place the rack in the lower middle position. Generously grease and flour two 9" nonstick cake pans. Tap out the excess flour and set the pans aside.

In a large bowl, whisk together the egg, oil, buttermilk, Bailey's, and coffee until fully combined. Set the mixture aside.

In another bowl, whisk together the flour, sugar, cocoa powder, salt, and baking soda until well mixed. Gradually add the dry ingredients to the wet mixture, stirring gently with a hand whisk until the batter is smooth and lump-free. The batter will be runny.

Pour the batter evenly into the prepared cake pans, ensuring even distribution. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Let the cakes cool completely in the pans.

While the cakes are cooling, place a metal mixing bowl and beaters in the fridge or freezer for 5 minutes to chill. Add the cold heavy cream, powdered sugar, and cold Bailey's to the chilled bowl. Beat on medium-high speed until the mixture forms stiff peaks.

If the dissolved gelatin has solidified, microwave it for 5-10 seconds until it becomes liquid again. Gradually drizzle the lukewarm gelatin into the frosting while continuing to beat on medium-high speed. Cover and chill the frosting until ready to use.

Once the cakes are completely cool, run a thin knife around the edges to loosen them. Carefully remove the first cake from its pan and place it on a serving plate. Frost the top with half of the frosting. Place the second cake on top and frost with the remaining frosting. Garnish with chocolate curls or chocolate chips, if desired. Store the cake covered in the refrigerator.