Preheat your oven to 350°F (175°C) and grease two 9-inch pans.
Whisk flour, cocoa powder, baking soda, baking powder, and salt in a large bowl.
Combine eggs, sugar, buttermilk, oil, and vanilla in another bowl until smooth.
Mix wet and dry ingredients, then gradually add hot water or coffee.
Pour batter evenly into pans and bake for 30–35 minutes.
Cool completely before frosting.
Frost with chocolate frosting using an offset spatula.
Melt white chocolate, transfer it to a piping bag or spoon, and drizzle in circular patterns.
Drag a toothpick from the center outward to create a web-like design.
Decorate with edible or plastic spiders. Chill for 15 minutes before serving.
