Preheat your oven to 350°F (180°C) and line a 24-cup cupcake tin with paper baking cups.

Whisk together 3/4 cup unsweetened cocoa powder and 3/4 cup hot water until smooth; set aside.

In a separate bowl, whisk together 3 cups all-purpose flour, 1 tsp baking soda, 1 tsp baking powder, and 1 tsp coarse salt.

Melt 1 1/2 cups unsalted butter with 2 1/4 cups granulated sugar in a saucepan over medium-low heat, then transfer to a mixing bowl.

Beat the butter and sugar mixture with an electric mixer on medium-low speed for 4-5 minutes until cooled.

Add 4 large eggs one at a time, beating until each is incorporated and scraping down the bowl as needed.

Stir in 4 tsp vanilla extract and the cocoa mixture, then reduce speed to low.

Gradually add the flour mixture in two batches, alternating with 1 cup sour cream, beating until just combined after each addition.

Fill each cupcake cup about ¾ full with batter (approximately ¼ cup per cupcake).

Bake for 20 minutes, rotating tins halfway through, or until a toothpick inserted into the center comes out clean.

Cool cupcakes in the tin for 10 minutes before removing, then cool completely on a wire rack before frosting. Cooled cupcakes can be stored overnight at room temperature.

Melt 1/2 cup unsalted butter in a microwave-safe bowl using 15-second intervals until completely liquid.

In a small bowl, combine 2/3 cup unsweetened cocoa powder, 1/2 tsp ground cinnamon, and 1/8 tsp chili powder; stir this mixture into the melted butter.

Melt 1 cup dark chocolate in a microwave-safe bowl with 20-second intervals, stirring between each, until completely smooth.

Add the butter-cocoa mixture and melted chocolate to a mixer with a whisk attachment; mix on medium speed for about 1 minute until combined, scraping the bowl as needed.

Alternate adding 3 cups powdered confectioners sugar (¼ cup at a time) and 1/3 cup milk (a few teaspoons at a time) to the mixer, beating on medium speed after each addition until a spreadable, shiny, and thick consistency is achieved. Add a little more milk if necessary.

Mix in 1 tsp vanilla extract for about 1 minute until combined, then set the frosting aside.

Roll out white fondant on a flat surface to about 1/8 inch thick, then cut out 24 two-inch round or scalloped circles.

Transfer the fondant circles to a parchment-lined pan and let them dry and harden for at least 10 minutes.

Using a black food-coloring marker, draw a dot in the center of each circle, then create at least 12 evenly spaced lines radiating outwards. Connect adjacent lines with semi-circles to form at least four spider webs.

To make 24 small spiders, color enough fondant gray with black gel coloring (use a toothpick for a small amount of gel).

Roll a pea-sized circle for the head and a bean-shaped body for each spider. Create eight small gray legs per spider and press them into the body to attach. Keep fondant covered with plastic wrap between uses.

Color a small amount of fondant orange with orange gel coloring for the spider eyes. Roll pinhead-sized circles for eyes and press them onto the spider heads.

Transfer each spider to a web, using a small amount of water on the bottom of the spider if needed to help it stick.

Using a large round piping tip, pipe 2-3 tablespoons of frosting onto each cooled cupcake.

Carefully place a fondant spider and spider web on top of the piped frosting on each cupcake.

Store assembled cupcakes for up to 3 days in an airtight container in the refrigerator, allowing them to come to room temperature before serving.