Preheat your oven to 350°F (175°C) and lightly grease a 9x13-inch baking pan with cooking spray.

In a large bowl, sift together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking soda, and salt.

In a separate bowl, whisk together the vegetable oil, vanilla extract, buttermilk, and boiling water until fully blended.

Gradually pour the wet mixture into the bowl with dry ingredients. Stir gently until just combined.

Pour the cake batter into your prepared baking pan and spread it evenly. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.

Once baked, let the cake cool completely in the pan on a wire rack.

While the cake cools, whisk together the granulated sugar, cocoa powder, and cornstarch in a medium saucepan. Gradually add milk, stirring until smooth. Heat and whisk until thickened.

Once thickened, remove from heat and stir in vanilla extract. Let it cool slightly.

In a large bowl, use an electric mixer to whip the heavy whipping cream with powdered sugar and vanilla extract until stiff peaks form.

Frost the cooled cake with whipped cream, then layer chocolate pudding on top.

Sprinkle crushed Oreos over the pudding layer and garnish with gummy worms.