In a large bowl, combine ground pork, eggs, chopped garlic, chopped shallot, half of the chopped onions, bread crumbs, nutmeg, and salt.
Shape the mixture into 1-inch balls.
Place flour in a small shallow bowl and dredge each meatball in the flour.
Sear Meatballs:
Over medium heat, heat 3 tablespoons of olive oil in a shallow earthenware casserole dish or Dutch oven large enough for all the meatballs to fit in one layer.
Add the meatballs and cook, turning occasionally, until browned on all sides.
Reserve.
Prepare Sherry Reduction:
Heat the remaining 2 tablespoons of olive oil in a small skillet over medium heat.
Add the remaining half of the chopped onions and cook, stirring, until wilted and transparent (about 5 minutes).
Add the sweet sherry, bring to a boil, and cook, stirring occasionally, until reduced (about 10 minutes).
Combine and Simmer:
Add the sherry reduction to the reserved meatballs.
Bring the mixture to a simmer over low heat and simmer for an additional 5 minutes.
Serve:
If using earthenware, serve hot in the dish, or transfer to a platter.