In a pan place the sliced onions and half the olive oil over a medium until soft, sweet and golden. Stirring regularly.
To clean the squid pull the head and tentacles away from the body. Cut off the tentacles and put aside for later. With your fingers, empty out the inside of the squid and discard. Gently pull the wings from the side and remove any pinkish membrane. Rinse under running water. Add the wings to the tentacles and chop.
In a frying pan heat the remaining oil and add the garlic, bay leaf and tentacles/wings and pancetta. Cook for about 5 minutes then add the sweet onions and the sherry and cook for another 15 minutes. Season then remove from the heat. Add the chopped egg, parsley and sumac. Cool mixture then stuff into the body of the squid leaving enough room to skewer the end together with a toothpick.
Put salt, pepper and a splash of olive oil over the squid and cook on a hot charcoal grill or bbq until golden.