Step 1

Preheat oven to 350 F / 175 C. Grease two, six-inch domed cake pans with non-stick spray or homemade cake release. Grease two heating cores and place in the center of the pans to help it bake more evenly and quickly. Place the pans on a baking sheet to help you easily move them in and out of the oven and set aside. If you want to use 8-inch domed cake pans, double this recipe and double the frosting recipe.

Step 2

Sift or whisk together the dry ingredients (flour, sugar, dark cocoa powder, baking powder, baking soda and salt) into a large bowl.

Step 3

Pour in the hot water, sour cream, oil, eggs, and vanilla into a separate bowl and whisk together until fully incorporated.

Step 4

Mix the wet ingredients into the dry ingredients just until they're incorporated into the batter.

Step 5

Divide the batter evenly between the prepared cake pans, making sure you fill the pans no more than 2/3 full. They will rise and can overflow if your pans are too full. Mine were about 1/2 way full. Bake for about 35-40 minutes or until a toothpick comes out with a few moist crumbs. Bake time can vary quite a bit based on your oven and if you use a heating core, so keep an eye on the cake once it's been in the oven for 35 minutes.

Step 6

Remove the cake layers from the oven and let them cool in the pans for about 10 minutes, then flip them into wire racks to finish cooling.

Step 7

Once cooled, use a serrated knife to level the top of each cake layer. Trim off about 1/2 an inch from the domed side of one of the cake layers. This will make it easier to stack the cake layers on your cake board. If make these in advance, wrap and freeze them at this point.

Step 8

Beat the butter on a medium speed for 30 seconds with a paddle attachment until smooth.

Step 9

Add in the vanilla extract and salt. Mix on low until the ingredients are fully incorporated.

Step 10

Slowly mix in the powdered sugar. Half way through, add in the heavy cream to make the frosting easier to mix. Place 1/4 cup of the white buttercream in a small piping bag fit with a round piping tip like Wilton 10 or cut a small opening in the bag that's about 1 cm wide. Set aside.

Step 11

Mix the melted dark chocolate, sifted dark cocoa, and black gel food coloring into the remaining frosting. Mix on a low speed until the ingredients are fully incorporated and the desired consistency is reached. Scrape the sides and bottom of the bowl as needed to make sure the buttercream is evenly colored.

Step 12

Place 2 Tbsp of black buttercream and cut a small 1/2 cm opening in the bag. Cover the rest of the frosting with plastic wrap to prevent crusting and set aside.

Step 13

Start by folding each of the bubble tea straws about 1/2 of the way down the straw and place in a large/ thick book to help them keep their shape. They need a bit of time (20-30 minutes) to allow them to stay bent once they're removed from the book.

Step 14

Stack and frost the cake layers on a greaseproof cake board. Use the cake layer with the trimmed dome first, sticking it in place with a dab of chocolate buttercream.

Step 15

Carefully spread an even layer of chocolate buttercream on top of the cake layer with an offset spatula.

Step 16

Stack the next cake layer on top, then freeze the cake for about 10 minutes in the freezer. This will help the buttercream between the cake layers firm up and make the cake easier to frost.

Step 17

Cover the cake with an even layer of chocolate buttercream and smooth using an acetate sheet or small offset spatula.

Step 18

Use the white and black buttercream to pipe two eyes onto the side of the cake.

Step 19

Place the rest of the black buttercream in a large piping bag fit with a large grass piping tip. Cover the cake with black buttercream to make our spider look fuzzy.

Step 20

Press 4 bubble tea straws on each side of the cake to look like legs, using tiny strips of clear tape to anchor the base of the straws to the edge of the cake board. Then enjoy!