Line a muffin pan with paper cupcake liners (hint: when I'm using plain paper liners, as opposed to the ones with an aluminium lining, I double them!). Pre-heat oven to 350 degrees F.
In an electric stand mixer, start beating egg and sugar on medium speed. While that is mixing, sift your dry ingredients: flour, baking powder, baking soda, cocoa powder, and salt in a bowl.
Add vegetable oil and milk into your egg and sugar mixture. Continue mixing.
Slowly add your dry ingredients to your wet ingredients, one third at a time. Mix thoroughly.
Once all of the ingredients are combined, add boiling water and mix. This will make the batter runny - exactly how you want it to be!
Pour batter into your lined muffin pan, about 1/4 cup for each section.
Bake 13-15 minutes and allow to cool on a wire rack.
With an electric mixer, beat butter, sugar, cocoa powder, and milk until smooth. Your buttercream frosting is complete once it forms semi-stiff peaks.
Using a piping bag, frost each cupcake. Top with chocolate chips and enjoy!