Makes 22 to 24 cupcakes
1 cup water
Step 1: For the cupcakes: Preheat oven to 350 degrees Fahrenheit. Line two standard cupcake pans with liners.
Step 2: In a small saucepan, bring water, vegetable oil, butter, and cocoa powder to boil. Whisk until smooth. Remove from heat and add semisweet chocolate. Whisk to combine until chocolate is melted. Set aside to cool.
Step 3: In a bowl, whisk together eggs, buttermilk, and vanilla extract. Slowly add cooled chocolate mixture to egg mixture.
Step 4: Sift together flour, sugar, baking soda, and salt. Add liquid mixture to flour mixture until just combined.
Step 5: Bake at 350 degrees for 20 to 22 minutes or until toothpick inserted in middle of cupcakes comes out clean.
Step 6: For the chocolate buttercream: Melt chocolate in microwave, stirring every 30 seconds.
Step 7: Butter butter, cocoa, and powdered sugar until light and fluffy