Step 1.

Make a new document 150x150 and fill it with any color. Make a new layer and usign the round rectangular tool with the settings below make a shape.


Step 2.
Add the folowing settings :

Inner shadow:



Gradient Overlay :



Stroke:



Step 3.
Next we need to make a selection like below. So press Ctrl+click on the button layer and using the poligonal lasso tool deselect the bigger part so it will look like my selection. Make a new layer and fill it white and lower the opacity to 40.



Step 4.
For a better effect I duplicated the layer and moved it a bit on the left. Then I made a new selection and filled it white. See below:


Go to Filter>blur>Gaussian Blur and add a 4.2 radius.



This is my final result:

Tutorial Source