Slugs will be extremely happy to live in your leaf mulch, fear not! I'd suggest that you invest in some organic slug bait (with iron phosphate as the active ingredient), and a few anti-slug activities such as beer traps, etc.

You could also rake up your mulch to expose some of the breeding habitat (a very yukky sight) so that you can have a 'salting'.

Slugs will enjoy any mulch - straw's sharper edges can actually deter them a bit. So slug treatments as rhizo suggests are the best approach.

Normal slug populations pose no real threat to the garden so the benefits derived from the mulch far outweighs any damage they do. But they can multiply rapidly, especially if the weather has been wetter than usual, so treatment is needed now and then to prevent a serious infestation.

Dave

My own slugs aren't particular;
they'll eat whatever the cafeteria's serving.

I never pour salt into the garden, & it really isn't necessary;
slugs will slurp up beer til they drown in it, & beer, unlike salt, is good for the soil!

You also can sprinkle diotomaceous earth (DE) or coffee grounds;
the sharp grains will cut & abrade slugs' slimy bodies.

Be sure to get agricultural DE;
the kind that you use in a swimming pool has been subjected to heat & its chemical structure changed so that it isn't good for garden use.

Best luck!

You have seen something that I also have seen, that slug damage to plants with only a straw mulch appears to be greater than where shredded leaves are used. Since I find the slug population is the same, because they need a cool, moist environment to exist, the conclusion I have come to is that the straw simply does not provide enough food while the shredded leaves do so the slugs do not need to munch on plants where shredded leaves are for that food source.
I also find that spraying plants that could be slug targets with cold, caffienated coffee (what is left over in the morning pot) is enough of a deterent to the slugs that there is no damage done. Because of that I have no reason to spend money, unnecessarily, on commercial products.