Last modified 19 February 2015
This one's really easy. The thing is, there's no reason to do it. You'll save a few pennies by buying the stuff in the store. But if you want something special, such as with some rosemary, you've pretty much got to do it yourself.
Note that "small amount" is easy to over-do. A half-teaspoon of salt is probably too much, for instance. You'll have to figure out how much to use based on how you like it and how much heavy cream you use. I usually get a quart of the stuff, so that's what my 1/2 tsp is based on. Still, that's probably too much. I don't add salt, as I want either sweet butter or herbed butter when I do this, and as I said at the top, doing this for sweet butter is only for the experience. Buying sweet butter is quicker, unless maybe you have a cow, but if you have a cow, you probably know more than I do about this and don't need this recipe.
I do this using a stand mixer with the whisk attachment, but you can do it in just about anything, like a large, sealable, container. If you use a container, you might watch TV while you do this.
The idea of the final step is that more of that liquid you dumped from the bowl or container is still in the butter. If the liquid is not removed, the butter will go rancid quickly. And I find my hand is nice and soft after massaging the butter. Since I'm a guy, this last bit is of dubious merit, but whatever.