The best attachment for creaming butter and sugar is a paddle attachment.
A paddle attachment is a flat, rectangular piece of metal with a rounded edge. It's designed to move ingredients around the bowl and incorporate air, which is essential for creating a light and fluffy texture when creaming butter and sugar.
Other attachments, like the whisk or dough hook, are not ideal for this task. The whisk is too thin and will not effectively incorporate air into the mixture, while the dough hook is designed for kneading and will overwork the butter and sugar.
When using a paddle attachment, it's important to scrape down the sides of the bowl periodically to ensure even mixing. You can also use a stand mixer or a hand mixer with a paddle attachment.