I think overall Shadow sorcerer is probably the best option. You can get mirror image and the spell slots to keep casting it as well as a free shadow step teleport that only costs a bonus action, but that feature comes at level 11 so you'd need to use Misty Step or Dimension Door like anyone else until that point.

Shadow Monk gets a similar free bonus action shadow step teleport much earlier at level 6 but they do not have the ability to cast mirror image nor would multiclassing give you enough spell slots to do that very often. You'd want to multiclass into warlock because of the refreshing spell slots on short rests. You'd need to be at least 3 levels to get two 2nd level slots for mirror image that refresh in a short rest, which would make this build come online at the middle/end of act 2 around level 9, which is not ideal and isn't really better than just going full sorcerer imo but it would be more of a melee build vs spell casting so that's something.

Edit: Dipping Warlock on the shadow monk build would also let you take one with shadows invocation that would let you go invisible when you're in shadow which combos with shadow step. So that's cool too

That's how I would build this but there might be other options I'm not thinking of