Soak prunes overnight in freshly brewed tea. Remove prunes from tea.
Make a slit down the length of each pork fillet and open out gently. Season inside with salt and pepper. Stuff six prunes with an almond and lay them on one fillet; cover this fillet by laying second opened fillet on top and tie fillets together firmly with a string. Season outside lightly with salt and pepper.
Brown fillets in the butter and oil on all sides. Remove meat, lower the heat and add the onions and brown gently for 10 minutes. Add the crushed garlic to the pan and cook slowly for 1 minute. Return the meat to pan and add the stock. Season lightly with salt and pepper. Cover the pan and simmer gently for 20 minutes. Pork should register about 155 -160° on a meat thermometer.
Meanwhile, place the remaining prunes and red wine in a saucepan. Simmer until tender and most of the wine has evaporated.
Remove meat and onions from pan. Allow pork to rest for 20 minutes. While meat is resting, add red wine reduction with prunes to the pork sauce in the pan. Bring mixture to a boil and if necessary, reduce to concentrate flavors. Remove the string. Slice meat and arrange on a hot serving dish.
Adjust seasonings, spoon sauce over meat, garnish with prunes and onions mixed together.
Serves 6 to 8.