Preheat oven to 350°F. Grease & flour three 4-inch cake pans. *See note below.

Sift flour, cocoa powder, baking powder, baking soda and salt together in a medium bowl. Add sugar and stir to combine.

Combine egg, buttermilk, vegetable oil and vanilla extract in a small bowl. Whisk lightly to combine.

Add egg mixture to dry ingredients and mix on low speed with a handheld electric mixer, until combined. Stop mixer. Scrape sides of bowl with spatula. Turn mixer up to medium speed and beat for 1 minute.

Add hot coffee and stir until incorporated.

Pour batter into prepared cake pans, dividing batter evenly between the pans. Bake for 20-25 minutes or until a toothpick inserted into the center of the cake comes out clean.

Cool cakes in pans 10 minutes, then invert onto a wire rack to cool.

Melt white chocolate in a double boiler over gently simmering water. (Alternately, you can melt the white chocolate in the microwave. In a small microwaveable bowl, heat the white chocolate for 30 seconds, then stir. Heat again for 10 second intervals, stirring until melted, being very careful not to overheat it.)

Set white chocolate aside to cool until lukewarm and still soft.

In a medium bowl, beat butter with an electric mixer at medium speed until pale and creamy.

Add vanilla extract, salt and melted white chocolate. Beat at low speed until combined. Stop mixer. Scrape sides of bowl with spatula.

Add powdered sugar. Beat at low speed, until powdered sugar is combined. Beat at medium speed until buttercream is smooth, stopping to scrape the bowl occasionally. Keep covered at room temperature until ready to use.

When cakes have cooled completely, trim the cake layers to 1-inch tall.

Attach one of the layers to a cake board with some of the white chocolate buttercream. Apply 1/4-inch thick layer of buttercream to the top of the cake layer, followed by the second cake layer, another 1/4-inch thick layer of buttercream, then the final cake layer.

Apply a crumb coat (thin layer) of buttercream to the cake. Chill the cake in the refrigerator for 20 minutes.

Frost the cake with the remaining buttercream. Apply chocolate sprinkles to the bottom edge of the cake.

Melt chocolate drip glaze ingredients together in a double boiler over gently simmering water. Let cool slightly.

Spoon chocolate glaze into a piping bag. Snip off the end of the bag with kitchen scissors. Drizzle chocolate glaze along the edges of the perimeter of the cake, then fill in the middle. Smooth top with a small offset spatula.

Top cake with assorted chocolate candy. If desired, you can stack some of the candy and adhere them with melted chocolate to give some variation in height.