Instructions:

• Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
• In a large mixing bowl, whisk together the melted unsalted butter, granulated sugar, and Greek yogurt until smooth. Add the whole egg, egg yolk, and vanilla extract, mixing until well combined.
• In another bowl, sift together the all-purpose flour, baking powder, and optional salt.
• Gradually add the dry ingredients to the wet mixture, folding with a spatula until just combined.
• Divide the batter evenly among the lined cupcake wells, filling each about 2/3 full. Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center comes out clean.
• Remove the cupcakes from the oven and allow them to cool in the pan for 5 minutes before transferring them to a cooling rack to cool completely.
• In a mixing bowl, beat the softened unsalted butter until creamy. Gradually add the sifted cocoa powder and confectioners' sugar, alternating with a splash of cream or milk until you achieve your desired consistency. Mix in the vanilla extract.
• Once the cupcakes are completely cool, use a piping bag or a knife to generously frost each cupcake with the chocolate buttercream. Top with chocolate sprinkles if desired.