Mix sauce ingredients in a small bowl. Set aside.
Cut piman in half, remove stems and seeds. Sprinkle flour inside piman with a mesh strainer.
Chop onion finely. In a large bowl, put onion, beef, pork, bread crumbs, egg, salt and pepper together and mix very well.
Stuff meat mixture into the piman.
Heat oil in a frying-pan at medium heat. Place the stuffed piman meat-side down in the pan and cook covered for 3-4 minutes. Then turn over and cook another 2-3 minutes until cooked through. Put sauce over meat and serve.