Instructions

• Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners and lightly spray the liners with non-stick spray; set the tin aside.
• Combine 2 1/2 tablespoons canola oil (or melted coconut oil), 1 stick unsalted butter (for the batter), and 1/2 cup semi-sweet chocolate chips in a microwave-safe bowl. Microwave in 30-second increments, stirring between increments, until melted and smooth. (Alternatively, melt together over very low heat on the stovetop.) Whisk until completely smooth and set aside to cool until warm but not hot.
• In a medium bowl whisk together 3/4 cup plus 2 tablespoons all-purpose flour (not packed), 1/2 teaspoon baking soda, 1 teaspoon baking powder, 1/2 cup unsweetened cocoa powder (sifted), and 1/2 teaspoon salt. Set aside.
• In a large bowl whisk together 2 large eggs, 1 large egg yolk, 1 cup granulated sugar, and 1 teaspoon pure vanilla extract until smooth.
• Add the cooled chocolate/oil/butter mixture to the egg mixture and whisk until smooth and combined.
• Add half of the dry ingredient mixture to the wet mixture and mix until just combined. Add half of the 1/2 cup buttermilk, mixing until just combined. Add the remaining dry mixture, then the remaining buttermilk, again mixing only until just combined. (Do not overmix.)
• Quickly stir in 1/2 cup hot water and mix just until the batter is evenly combined.
• Divide batter among the prepared liners, filling each about 3/4 full. (You may have enough batter to make more than 12 cupcakes; bake remaining batter in additional tin(s) as needed.)
• Bake at 350°F for 16–18 minutes, or until a toothpick inserted in the center of a cupcake comes out clean. If baking multiple batches, repeat as needed.
• Let cupcakes cool in the tin for a few minutes, then transfer to a wire rack and cool completely before frosting.
• For the frosting: sift together 3 cups confectioners' sugar and 3/4 cup unsweetened cocoa powder into a bowl and whisk to remove any lumps.
• In a stand mixer fitted with the paddle attachment or with a handheld mixer, beat 1 stick unsalted butter (for the frosting) on medium-high speed until creamy, about 2 minutes.
• Reduce mixer speed to low. Slowly add the sifted sugar/cocoa mixture in portions, alternating with 3 to 4 tablespoons well-shaken buttermilk, and add 1/4 teaspoon salt and 1 teaspoon vanilla. Use the 3–4 tablespoons buttermilk as needed to reach a spreadable consistency.
• Once all ingredients are added, increase mixer speed to high and beat for at least 1 minute, until the frosting is light and creamy.
• Frost the cooled cupcakes. Store cupcakes at room temperature in an airtight container for up to 4 days.