Have you ever tried to add salt to unsalted butter? [View all]

[Paper Roses]

A neighbor just moved and gave me some refrigerated foods that she did not want to take with her.
I now have a 1 pound block of unsalted butter.
I Googled to see if there was some way to add salt and the answers left me a little puzzled.

Have you ever done this?
It is cold here and I really don't know how to soften the block of butter that will not melt it. If the weather was warm, no problem. My heat is not on yet and it is 64 degrees in the kitchen, not enough to soften the butter.

The advice was to add 1 teaspoon salt to a pound of softened butter.
That seems a lot to me. If this is right, should I use a mortar and Pestle and pulverize the salt?

I know I would have to mix it well and then mold and quarter the butter to freeze it.
This may seem silly but I don't want to waste it and butter is almost $5.00 a pound here so it would be worth the time.
Any ideas?
Thanks