Add the egg yolks, granulated sugar, lemon juice, and lemon zest to a saucepan. Cook over low heat, stirring constantly, until thickened. Add the butter and stir until smooth, then strain and let cool completely.
Add the softened butter and powdered sugar to a mixing bowl.
Add vanilla extract and Mix until light and creamy.
Add the heavy cream, and salt.
Beat until smooth, fluffy, and creamy. Set aside.
Add the softened butter and granulated sugar to a mixing bowl.
Mix until light and creamy, then add the eggs and mix well.
Add the lemon zest and mix until well combined.
In a separate bowl, whisk together the all-purpose flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture and mix gently.
Add the milk and mix until just combined.
Add the lemon juice and mix until the batter is smooth.
Divide the batter evenly among the lined cupcake cups.
Bake at 180°C (350°F) for 18–21 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool completely. and make a small hole in the center of each cupcake.
Fill with the cooled lemon curd.
Pipe the prepared vanilla buttercream over the cooled cupcakes.
Decorate with lemon slices or mint sprigs, if desired. Serve and enjoy.
