Attack Move to Attack Enemy Champion?

I've recently figured out (sort of) Attack move by using the .ini remap to me left mouse button. I can already tell after two games that this is going to be a game changer for me.

The issue is that whenever I get into a fight where enemy minions are around, I will immediately start attacking them instead. I can't count the number of times before this I would shift click while running down a fleeing enemy and then whack the nearest mob. :(

I'm sure there's an answer here, anyone? Thnks!