The BBC program "Bang Goes the Theory" (
http://www.bbc.co.uk/iplayer/episode/b00p8469/Bang_Goes_the_Theory_03_12_2009/) managed to cook a chicken using 2 filament bulbs - to demonstrate how much energy was wasted.
They used a box of 6in thick polystyrene, foil lined with 2 bulbs inside. After 90 minutes the chicken was cooked and edible.
So I thought.......build such a box with a copper coil/heat sink inside. Pipe in solar hot water which can get to 93C in February and beyond boiling in Summer. With good insulation all you need to do is get the food hot, then balance heat loss.
The power available from a solar thermal panel is huge compared to 2 light bulbs, so the idea is quiet achievable.
Bacteria is killed at 66C, 82C in a chicken thigh is considered safe. Solar can easily achieve those temperatures.
My other idea is a very well insulated electric slow cooker - 150 Watts of PV might be enough.
Mad or what?

cheers
Paul