Is the backsplash already installed and the electrical finished. If it is still under construction I would change the outlets to plug strips and mount them under the cabinets with a power bar. You will need to add a 1" strip to the bottom of the cabinets to hide the power bar. You can see pictures of this on my profile.

If construction is completed I would use painters caulk on the gap and paint it to match the face plate. Don't go to crazy with the caulk if you ever need to cut it and remove the face plate.

Yes, the electrical is already in and this is part of a remodel. I wondered about using some kind of caulk and you affirmed that this could be the solution. Do the existing electrical boxes need to be built out? The stacked stone is approximately 1/4" thick. Thank you for helping me out.

Oh, what wonderful information. Thank you so much for your expertise. I checked out your project pictures. Looks like beautiful work. Too bad you are clear across the country from where I am!

For anyone thinking of putting outlets up underneath the upper cabinets, please don't. Check with your local electrical inspector first. It does not meet code and most inspectors won't allow it. Second, a slip in box extension may not be necessary for box depth, depending on exact situation, but is necessary in the sense that caulk is not allowed inside the electrical box. It will also make it easier to mold the caulk without squeezing it into the box.

I have never had a problem with any city inspector and the power bars meeting code. The only code requirements pertaining to kitchen outlets is that there has to be at least 2 circuits to the kitchen, need an outlet for every 4' of countertop, and it has to be GFCI protected. Is there another code I am missing?

Yes, it says at counter height. I believe the new code books have a fpn saying how far that is.

Interesting, I will have to look into that.

I just looked up a California specific, not NEC, and it looks like it is ok there. We have never been able to get away with more than 12" here.

So here is what I found. I am in California so this code may be different where you are.

I was wrong earlier about every 4', it should be every 2' on a countertop but I don't see anything that would prevent you from installing plugs to the underside of the cabinet. Let me know if you find any information that does say this.

Here is the link: http://www.fremont.gov/DocumentCenter/Home/View/7164

It says that no place shall be more than two feet from an outlet, which means outlet every 4 feet. Can't seem to find the link where I thought I read California was 20" above counter.

That sucks. Outlets are always such an eye sore in a backsplash. Hopefully it changes for you in the future.

Yea, I wish, new guy is worse than the old inspector.