<div class='box'></div>

.box { /* these are all the essential styles */
  overflow: hidden;
  position: relative;
  margin: .25em auto;
  max-width: 15em;
  min-height: 10em;
  border-radius: 1em;
  
  &:before {
    position: absolute;
    margin: -3em;
    padding: 3em;
    border-radius: 50%;
    box-shadow: 0 0 0 300px rgba(#95a, .75);
    content: ''
  }
}

/* JUST PRETTYFYING STUFF, NOT ESSENTIAL FOR A WORKING DEMO */
html {
  $over-c: rgba(invert(#222), .5);
  min-width: 10em; height: 100%;
  background: 
    linear-gradient($over-c, $over-c), 
    url(https://images.unsplash.com/photo-1510920018318-3b4dfe979e4d?ixlib=rb-0.3.5&q=80&fm=jpg&crop=entropy&cs=tinysrgb&w=1080&fit=max&ixid=eyJhcHBfaWQiOjE0NTg5fQ&s=76eda3022d9860f69a7fc7a94e46c3e6) 0 0/ cover
}