1. Start off with a new document, 300 by 300
Grab your paint bucket tool and fill your stage with black or dark gray color. Choose any color for your button it doesn't matter

2. Using the tool box, select the rounded rectangle tool and draw the size of you button.

Double click on the layer " button" and the layer styles menu should open. First - select true glass gradient colors.
I’ve used : #656a6d - #000000; #434343 - #dedede;

The next step - apply another inner stroke, since it’s impossible - we’ll use “Inner Glow”

Yout finish, I hope you get the result I did. Good Luck