Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.

In a large mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.

In a separate bowl, beat the eggs, granulated sugar, vegetable oil, and vanilla extract until well combined.

Gradually add the dry ingredients to the egg mixture, alternating with the milk. Begin and end with the dry ingredients, mixing just until combined after each addition.

Stir in the boiling water until the batter is smooth. The batter will be thin.

Pour the batter into the cupcake liners, filling each about two-thirds full.

Bake in the preheated oven for 18 to 20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.

Remove the cupcakes from the oven and let them cool in the muffin tin for about 5 minutes. Then, transfer them to a wire rack to cool completely before frosting.

Then, make the chocolate buttercream frosting.  In a large mixing bowl, beat the softened butter until creamy and smooth.

Gradually add the powdered sugar and cocoa powder, about 1 cup at a time, mixing well after each addition.

Add the milk, one tablespoon at a time, until the desired consistency is reached. Stir in the vanilla extract and mix until well combined.

Once the cupcakes have cooled, frost them with the chocolate buttercream frosting using a piping bag or spatula.

If desired, decorate the cupcakes with sprinkles, chocolate shavings, or any desired toppings.

Lastly, serve and enjoy these delicious Chocolate Cupcakes!