May 30, 2018
This method comes in handy if you’re working with plugins and are unable to edit theme files, or external files at the risk of losing your styles with an update.
.double-border {
border-radius: 50px;
background: #fff; /* background */
border: 5px solid transparent; /* border one */
box-shadow: 0 0 0 1px white; /* border two */
height: 25px;
width: 25px;
-moz-background-clip: border;
-webkit-background-clip: border;
background-clip: border-box;
-moz-background-clip: padding;
-webkit-background-clip: padding;
background-clip: padding-box;
-moz-background-clip: content;
-webkit-background-clip: content;
background-clip: content-box;
}
Sources:
How to Double Border and Border Radius Demo
Transparent Borders with Background-Clip
