finely mince the ground beef and pork and mix well in a large bowl. Using hands works best.
Add the pancetta, breadcrumbs, shallot, salt, pepper and sour cream. Mix well, again hands works best.
Filling
In a fry pan place the butter over medium low heat. Once it is melted and hot add the onions and mushrooms. Saute until soft, translucent then add the garlic. When garlic is fragrant add the breadcrumbs and mix well. Once well mixed remove from the heat.
Add the sea salt, white pepper, nutmeg and coriander. Mix well and let coll to room temperature.
Whisk together the sour cream (or yogurt) and egg in a small bowl, whisk well.
Add the egg/sour cream to the mushroom mixture.
Set aside.
Assembly and cooking
Using about ¼ cup of the meat mixture in your hand. Flatten the ball into a disc and form a disc.
Add 2-3 tsp of the filling on top of the meat disc. Bring up the edges of the disc covering the filling.
Place the filled meatballs on a parchment covered cookie sheet.
Place the EVOO in a fry pan over medium low heat. When shimmering and hot add the filled meatballs and brown.
Do not overfill the fry pan. Once you have browned all the meatballs, place them back into the skillet.
Add the chicken stock, bay leaf, onion into the skillet. Simmer for 30 minutes until the meatballs are well cooked.
Gravy and serving
Remove the meatballs with a slotted spoon and place them into a bowl.
Pour all the juices in the pan into a mixer and blend thoroughly. Add the flour and blend again.
Place the blended gravy back into the skillet and heat until it thickens.
Add the sour cream and whisk well. Add the salt and pepper and whisk again.
Place the filled meatballs back into the bravy and heat.
Serving the meatballs, sprinkle with shopped parsley.