Construct Half Wall
Build your wall up like any normal half wall and make sure you have a secure mount to your king stud and subfloor (floor joists if possible). The double top plates probably weren't necessary.
Screw 3/4" plywood into all the studs, especially the king stud and the floor plate. I even ran some long deck screws diagonally down through the floor plate and into the sub floor. 3/4" thick probably isn't necessary. You could probably get away with 1/2" if you're trying to keep the wall thinner.
After all your electrical is ran, skin the other side in plywood making sure you have a nice solid mount to your king stud and floor boards. I know this won't give you the best accessibility for electrical mods down the road but I know no other way unless you're okay with a slightly wobbly wall.
Test out the rigidity of your half wall by drinking a beer on it.
I really wanted a sturdy bar top for it (and I didn't know if I was going to use quarbles or not yet) so I designed a 12 gauge sheet metal bracket to mount the butcher block top to. I have 2 more of these if anyone wants them. Or I can send you the CAD drawing...
Shim the bracket to make sure it's level. (Plywood removed so I could install T-nuts for the corbels I decided on using.)
Fully install the bracket to make sure everything's level. I had to notch channels in the top plate for the bracket flanges.
Corbels test fit so I could pre drill the holes and install the T-nuts in the back of the plywood. This is probably not the best way of doing this but once again, I wanted to make sure it'd be strong and not just a pointless aesthetic piece.
Remove everything, reinstall plywood, attach drywall, mud and paint.
Bolt bracket back up, once again making sure all is level.
Stain and install butcher block.
Installed trim, filled and sanded the holes. You'll notice this of course eliminates my ability to remove the butcher block later. Oh well, wanted it strong...
All caulked and painted (with electrical protector bracket installed).
So yeah, nothing too fancy. It's sturdy (I danced on it - no wobbling) and doesn't take up much room. Here's a finished picture with the electrical covered.