JSFiddle - React, Tailwind, and code Playground

HTML

<div class="map_infobox">
    <div class="title">Title goes here</div>
</div>

CSS

body {
    background: blue;
}


.map_infobox {
    margin: 30px 0 0 30px;
    position: relative;
    background: #FFF;
    border-radius: 10px; 
    width: 250px; 
    height: 250px;
    border-opacity: 0.3;
    border: 5px solid rgba(0, 0, 0, .2);
    -webkit-background-clip: padding-box; /* for Safari */
    background-clip: padding-box; /* for IE9+, Firefox 4+, Opera, Chrome */
}

.map_infobox:before{
    content: "";
    position: absolute;
    top: 50%;
    left: -35px;
    z-index: 1;
    height:60px;
    width:30px;
    margin-top: -15px;
    background: linear-gradient(-45deg, white 17px, rgba(0,0,0,0.2) 17px, rgba(0,0,0,0.2) 21px, transparent 21px), linear-gradient(225deg, white 17px, rgba(0,0,0,0.2) 17px, rgba(0,0,0,0.2) 21px, transparent 21px);    
    background-position: left 0px, right bottom;
    background-size: 100% 50%;
    background-repeat: no-repeat;
}

.map_infobox:after{
    content: "";
    position: absolute;
    top: 50%;
    left: -35px;
    z-index: 1;
    height: 48px;
    width:30px;
    margin-top: -14px;
    border-right: solid 5px white;
    border-top: solid 5px transparent;
    border-bottom: solid 5px transparent;
}