Mix the ground meats, ricotta, parsley, panko crumbs, onion, pecorino, bacon, garlic, milk, thyme, egg, salt, Worcestershire, and black pepper, to taste, in a large bowl.
Mix until just combined; don't overmix. The mixture will be pretty soft.
Using your hands, gently form mixture into 1 tablespoon small meatballs (about the size of ping pong balls).
Put them on a large plate or pan; cover and refrigerate at least an hour or up to 24 hours.
Heat the oil in a medium nonstick skillet over medium-high heat.
Add about 1/3 the meatballs and cook, turning occasionally, until well browned on all sides, about 6 minutes.
Transfer the meatballs to a plate and repeat with the remaining meatballs.
Drain off the oil and wipe out the skillet. Return the meatballs to the skillet and pour in the marinara sauce. Bring to a boil, lower the heat, cover, and simmer until the meatballs are cooked through, about 15 minutes.
Serve the meatballs, skewered on a platter with a dollop of the sauce and a fresh leaf of basil. They can be serve warm or at room temperature.
The meatballs can be stored, covered, in the refrigerator for 3 days, or frozen for up to 6 weeks.
