So my setup seems a little complicated, it requires three components, but it provides a very stable mount that works for pretty much any phone and two of the components can be moved from car to car.
First I get a car specific mount from proclipusa.com. You have to be sure and order one for your exact year, model, etc., especially with the Mini as it varies based on your center display. The ProClip mounts come with adhesive, but you typically don't need it, they grip the part they mount on quite securely. I've used them in four or five cars now and have been quite happy with them.
Then get these two components: https://www.amazon.com/ARKON-Mount-Installation-Pattern-Garmin/dp/B00SV2M1X8 https://www.amazon.com/Midsize-Tablet-Holder-iPhone-Galaxy/dp/B00JCW8D38
Or instead of those two components, get a 17mm ball mount like this: https://www.amazon.com/Akron-4-Hole-AMPS-G-Ball-Adapter/dp/B01F9BEQDQ/ 17mm is a fairly standard size for these things. Garmin used it for a lot of their GPS devices, and there are a lot of phone holders that work with it. A lot of suction cup mounts like this: https://www.amazon.com/Arkon-Holder-iPhone-Galaxy-Retail/dp/B00I58VAZS/ Use a 17mm ball. You can even find some wireless charging phone bases that use the 17mm mount.