To maintain your daily helping at the most appropriate temperature...
the table in question would have a number of placemats embedded into its surface. Each placemat would be made of a conductive material (metal, stone) and be drilled to act as a heat exchanger.
Through the placemat would
pass a conductive fluid (oil) pumped via small pipes (also embedded into the table surface) across a heating/cooling element. The element would constructed from a peltier device and a switch to alter the oil flow across either the hot or cold face.
The user would set the desired hotplate temperature by using a hall effect based slider (not contact, magnetic field sensing replacement for a normal mechanical based slider) placed above the placemat.
This system could be extended to the drinks coasters, to allow your alchoholic beverage to be served and then remain nicely chilled.
Note: The table may require a large radiator hidden beneath its surface to dissapate excess heat when the peltiers are used in a cooling mode. A second coolant circuit would flow through the peltier units and would be switched to the opposite peltier face of the placemat coolant.
The design is in a minimal style, where the end result should contain no obvious technological elements.