Preview Mail Notification in browser

With Laravel, according to the documentation, I can return a Mailable via a controller to display it in the browser. It helps to preview mails.

Is there a way to preview Mail Notifications in browser?

I tried:

return (new MyNotification())->toMail($some_user);

But it does not work:

The Response content must be a string or object implementing __toString(), "object" given.

via Chebli Mohamed