Finish the following sentence with the best choice: How do I cream butter to make butter cookies?

Choices:
- To cream butter for butter cookies, mix the butter, sugar, egg yolk, vanilla and salt in a mixer until liquid.
- To cream butter for butter cookies, mix the butter, sugar, egg yolk, vanilla and salt in a mixer until light and fluffy.

Answer:
To cream butter for butter cookies, mix the butter, sugar, egg yolk, vanilla and salt in a mixer until light and fluffy.