I took a wall-wart power supply, said to output 9Vdc, 1A max. I measured it under load to be at 10.3Vdc. So with my surplus power resistors summing up to 12.7 ohm, I could drive the LED at about (10.3-5.9)/12.7 = 0.34A (measured 0.32A).
The result is shown in a short youtube video, composed of few pictures.
As a practical result, the sink area is very well lit even at just 2W input. The cold white light gives an unreal look to the inox sink, but colors are not distorted.
The heatsink has been equipped with two thin magnetic strips (superglued), so that the installation is not permanent.