<div>
  Кнопка
</div>

div {
  background-color: #fc7;
  width: 100px;
  height: 40px;
  line-height: 40px;
  font-size: 20px;
  text-align: center;  
  margin: 0 20px;
  position: relative;
  cursor: pointer;
}

div:before {
  content: '';
  display: block;
  background-color: #fc7;
  height: 28.5px;
  width: 28.5px;
  transform: rotate(45deg);
  transform-origin: top left;
  position: absolute;
  top: 0;
  z-index: -1;
}

div:after {
  content: '';
  display: block;
  background-color: #fc7;
  height: 28.5px;
  width: 28.5px;
  transform: rotate(45deg);
  transform-origin: top left;
  position: absolute;
  top: 0;
  left: 100%;
  z-index: -1;
}