Any real wood (or plywood) top of 1 inch nominal will be more than enough to support the small amount of cantilevered mass you have here. This is true even if it was not attached to the underlying table. Heck, even some of that Ikea foam-core stuff would probably be ok.
Your only concern at these dimensions is if the cantilevered mass will want to deform the material in the middle, causing it to warp. Maybe some poorer quality aggregates would do this, especially as they age.
If you do fasten it to the table with glue and metal fasteners, it isn't going anywhere. You could even use 1/2 or 3/4 inch plywood in this case.
Search the previous Q&A for references to the "sagulator" which can give you some idea of how wood deflects. But you can get a good feel for this simply by taking your material, overhanging 12cm over the edge of your workbeanch, and pressing on it with your hand. The amount of deflection you get, and how it bounces back gives you all the information you need.