UserControl doesn't support templates, so I don't think it's suitable for what you are trying to do here.
Create a custom control using the wizard. The button goes in the template for your custom control that is created in Generic.xaml
Since it sounds like you want to create something similar to a UserControl, I would change the base class from Control to ContentControl.
HTH
>Hey Viv,
>
>Revisiting this topic...
>
>I get how to subclass the control. The question is how do you put a button on the base class?
>
>Thanks