Preheat the oven to 150 deg C.
Toast the cumin seed and the caraway seed in a dry frying pan over a medium heat until the spices start to pop or you can smell them, no more than a couple of minutes. Grind them in a pestle and mortar or a spice grinder. In a lidded pot that is good for the hob and oven (like a dutch oven or similar), add the ground spices to the pork along with the paprika, garlic, bay leaves, stock and amontillado. Add some salt and pepper (not too much, you can add more later if you need to), and stir it all through. Bring to the boil. Cover and place in the oven for 2 hours.
Remove the lid and put it back in the oven. You want to evaporate off any excess fluid, retaining the flavours of the amontillado and the stock in the meat. When the rillettes are done, the meat will be firm but yielding. This will take 2.5 – 3 hours depending on your oven, pot, etc!
When the rillettes are ready, remove the pan from the heat. Remove the meat to a plate where you can pull it apart with forks (as you would with pulled pork). Put in a sterilised jar or dish that you will use for your picnic, packing it in. Pour some of the fat on top, which will add flavour, moisture and seal the rillettes so that they keep longer.