Bring a big enough pan of water to the boil and add 1tsp salt.Place the pork knuckles into the boiling water. Bring to the boil again and simmer for 15 minutes. Lift carefully out of the water and place them in a baking tray with baking paper on the bottom. Keep the water aside.Preheat oven to 160C.Mix olive oil with paprika, cumin, ginger, cinnamon, crushed garlic, and 1tsp salt. Rub the knuckles the mixture. Place the knuckles into a baking pan and pour beer over them and roast for about 1 hour. If necessary add more water or beer, so that the bottom of the pan is always covered with liquid.If you want the fat very crispy, sprinkle every 15 minutes with salt water.In a deep pan fry the onions with little cooking oil, add chopped tomatoes, not too much water from the pork knuckles and potatoes. Cook for 10-15 min or until potatoes are cooked.Serve with potato stew and green salad. Sprinkle with thyme