supernovi wrote:clearly something is adding a prefix to the directory string.
This "something" ought to be a previously installed software (WordPress, Joomla or whatever), which puts a .htaccess file into your htdocs and may do some redirections. And it does not expect a "base" subfolder in that context. Thats what i believe what happens.
Anyway, it is never a good idea to run a VirtualHost in a subdirectory of the DocumentRoot (i.e. the htdocs folder). Put the the VirtualHost to the same level as the htdocs folder (at least), so they cannot collide. For example, use /Applications/XAMPP/xamppfiles/base instead of /Applications/XAMPP/xamppfiles/htdocs/base. Or /Applications/XAMPP/xamppfiles/VirtualHosts/base (so you can easily see, which VirtualHosts you have on your system).