Icon color in button-icon

I have a question that extends from this question.

I have a "FAB-esque" button ala Material Design and when I click this "button", an ionicModal launches.
Button:

<my-directive class="button button-icon assertive ion-plus-circled button-floating-action"></my-directive>

The problem came when I tried to add some shadow to this thing.
Box-shadow doesnt work because it creates a ghost-box. But text-shadow works. Here's the custom css:

.button-floating-action {
    position: fixed;
    top: calc(90vh - 50px);
    right: 2vw;
    z-index: 999;
    text-shadow: 5px 5px 5px #888888;
}

The "+" isn't white but transparent which means the shadow is seen through and looks funky.
Anyway to enforce the icon color vs the background color (white and red respectively)
The funky button-icon:

Thanks!