Slice bread all the way through top to bottom, make slices about 1- 1 1/2 inches thick, set aside.
Put all ingredients in Food processor, blender or use an immersion blender with everything in a bowl or 2 cup glass measuring cup (this is my favorite method, the blender is my last choice). Zizz everything up until there are no more chunks of anything. Taste the mix and adjust - some garlic is mild some have more bite - you want a good strong garlic taste. The mix will be kind of soupy, it firms after chilling if you have leftovers - when you go to use it again let it soften a few minutes until spreadable.
If you add cheese you might not want to add the salt, especially if you use the kind in a can - I usually add fresh and like it with a little salt. Though the cheese can cause a little sticking on the grill, it tastes great and worth a little clean up.( If doing this in the broiler - don't add the cheese to the mix - but sprinkle it on the bread after you turn it over and broil till toasty. ).
Spread a nice thin coat of butter mix on both sides of you bread. I usually stack them on a cookie sheet if I'm using the whole loaf - for just the two of us I use 4 slices and save the rest for another day.
I usually grill the bread when everything else is almost done, cooking time varies with your grill and whether you're using gas or charcoal.
Put the bread on the grill, check it often you want it kind of golden toasty or a little darker - sometimes the edges get over cooked in spots it's ok . Move the bread around as needed to keep from burning, My gas grill is hotter in the center so I have to spin the bread on the edges to keep it even - grill both sides of the bread, it usually takes a couple of minutes per side, serve ASAP Great with wine or a cold beer - I like to dip it in barbecue sauce.
Remember - this is flexible - you can leave out all the extras except for the garlic - or add other seasonings like oregeno. Enjoy!
Important - Use the butter mix within a week or freeze the leftovers.