JSFiddle - React, Tailwind, and code Playground

HTML

<div id="bubble">
    <p>This is madness!</p>
</div>

CSS

#bubble {
    width:200px;
    height:100px;
    border:1px solid #000;
    position:relative;
    -moz-border-radius:20px 20px 20px 0;
}
    #bubble p { 
        margin: 1em; 
        font-family:Comic Sans MS;
    }
#bubble:before {
    content:'';
    width:20px;
    height:20px;
    background:#fff;
    border-left:1px solid #000;
    position:absolute;
    top:100px;
    left:-1px;
    z-index:1;
}
#bubble:after {
    content:'';
    -moz-border-radius:20px 0 0 0;
    border:solid #000;
    border-width:1px 0 0 1px;
    width:20px;
    height:19px;
    position:absolute;
    top:100px;
    left:0;
    z-index:1;
}