Yields 48 meatballs
Combine the red wine, port, shallots, bay leaves, thyme, peppercorns and bacon in a medium saucepan. Bring to a simmer over medium-high heat, reduce the heat to medium and cook until reduced by one-third, about 30 minutes. Add the chicken broth and continue cooking until reduced by half, about 40 more minutes (you should have about 2 cups liquid). Strain into a clean saucepan.
Mix the butter and flour in a bowl to form a paste. Whisk the paste into the sauce and simmer over medium heat, whisking, until slightly thickened, about 10 minutes. Whisk in the heavy cream and season with salt. Set aside.
Pulse the bacon and onion in a food processor until finely chopped. Transfer to a bowl and add the beef, breadcrumbs, parsley, egg, garlic, mustard, Worcestershire sauce, 3/4 teaspoon salt and 1/2 teaspoon pepper; mix until just combined. Dampen your hands and form into about 48 meatballs, 1 inch each.
Heat the vegetable oil in a large nonstick skillet over medium heat. Working in batches, add the meatballs to the skillet and cook, turning, until browned and cooked through, 5 to 7 minutes. Drain on a paper towel-lined plate.
Wipe out the skillet, add the sauce and the meatballs, and cook over medium heat until the sauce is simmering and the meatballs are heated through, about 2 minutes. (Add 1 to 2 tablespoons water if the sauce is too thick.) Top with chives.