For the Cupcakes:

1. Heat the oven to 350°F (175°C) and line a muffin tin with cupcake liners.
2. In a large bowl, sift together the flour, sugar, salt, baking soda, and baking powder. Whisk well to combine.
3. Separate the eggs, setting the yolks aside for another use, such as custard or French buttercream.
4. In a separate bowl, whisk all the wet ingredients until smooth. The mixture may look slightly lumpy — this is completely normal.
5. Pour the wet mixture into the dry ingredients and stir just until blended.
6. Spoon the batter evenly into the prepared liners, filling each about two-thirds full.

7. Bake for 18 minutes, or until the centers spring back lightly when touched. Let cool completely.

For the Buttercream:

1. Using a stand mixer fitted with the paddle attachment, beat the softened butter until smooth and creamy.
2. Gradually add the powdered sugar in two portions, mixing well after each addition.
3. Add the salt, milk, cream, and vanilla extract, then beat until light, fluffy, and smooth.
4. Spoon the frosting into a piping bag and pipe generous swirls onto each cooled cupcake.