Step 1: Preheat the Oven - Start by preheating your oven to 350°F (175°C) and lining your cupcake pan with parchment liners.
Step 2: Melt the Butter - In a medium saucepan, melt one stick of unsalted butter over low heat until fully melted. Remove from heat and let it cool slightly.
Step 3: Combine Wet Ingredients - In a large mixing bowl, whisk together the melted butter, coconut or canola oil, and granulated sugar until well combined. Add in the eggs, egg yolk, and vanilla extract. Mix until smooth.
Step 4: Melt the Chocolate Chips - In a small bowl, melt the semi-sweet chocolate chips in the microwave in 20-second intervals, stirring after each until fully melted. Let it cool slightly before adding it to the wet mixture.
Step 5: Mix Dry Ingredients - In another bowl, whisk together the all-purpose flour, baking soda, baking powder, cocoa powder, and salt.
Step 6: Combine All Ingredients - Add the dry ingredients to the wet mixture, alternating with the sour cream and hot coffee or water. Begin and end with the dry ingredients, mixing until just combined.
Step 7: Fill the Cupcake Liners - Evenly distribute the batter into the cupcake liners, filling each about ¾ full.
Step 8: Bake - Bake in your preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool in the pan for 5 minutes before transferring to a cooling rack.
Step 9: Make the Frosting - In a medium bowl, beat one stick of unsalted butter until creamy. Gradually add confectioners’ sugar, cocoa powder, sour cream, milk, salt, and vanilla extract. Beat until smooth and fluffy.
Step 10: Frost the Cupcakes - Once the cupcakes are completely cool, frost them generously with your chocolate frosting using a piping bag or spatula.
