In a large bowl, whisk together ¼ cup water, the breadcrumbs, eggs, grated garlic, parsley and ½ teaspoon each salt and black pepper. Add the beef and pork, then mix with your hands until thoroughly combined. Divide into 20 portions (about 2 tablespoons each) and place on a large plate. Using your hands, form each into a smooth ball. Refrigerate, uncovered, for 1 hour (the meatballs can be refrigerated up to 12 hours, covered).

In a 12-inch skillet over medium, heat the oil until shimmering. Add the meatballs and cook, turning occasionally, until browned on all sides, about 10 minutes. Return the meatballs to the plate and set aside.

To the fat remaining in the skillet, add the sliced garlic, the anchovies, rosemary sprigs and pepper flakes. Cook over medium, stirring, until the anchovies have broken down and the mixture is fragrant, about 1 minute. Reduce to low, then add the broth, followed by the wine. Bring to a simmer over medium-high and cook, scraping up the browned bits, until the liquid has reduced by about half, 5 to 8 minutes.

Add the meatballs and any accumulated juices to the pan, along with ½ cup water. Cook, uncovered and occasionally swirling the pan, until the center of the meatballs reach 160°F, 7 to 10 minutes.

Remove and discard the rosemary sprigs. Add the minced rosemary and vinegar; cook, stirring, until the sauce is slightly thickened and reduced, about 2 minutes. Remove from the heat, then taste and season with salt and black pepper. Serve sprinkled with additional chopped parsley.