Heat oil in a saucepan over medium heat. Soften onion for 5 minutes, then add beef and cook for 7 to 8 minutes, breaking it finely, until no pink remains and it reaches 160°F. Add garlic for 1 minute.
Stir in lentils, passata, broth, oregano, salt and pepper. Simmer partly covered for 18 to 22 minutes, stirring frequently, until the lentils soften and the sauce is thick; uncover briefly if needed to reduce to about 4 1/2 cups.
Heat oven to 375°F. Butter twelve jumbo muffin wells of about 6 ounces each, using two pans if needed. Overlap two wonton wrappers in each well to cover the bottom and sides.
Add 3 tablespoons sauce, 1 tablespoon ricotta and a little mozzarella to each. Press one more wrapper over the filling, then repeat with remaining sauce, ricotta and mozzarella, dividing evenly.
Bake for 20 to 24 minutes until hot through and browned at the corners. Rest for 10 minutes, loosen carefully and lift out; refrigerate in shallow containers within 2 hours.
Freeze the chilled cups on a lined tray until firm, then wrap individually and bag for up to 2 months.
Reheat two frozen cups on a microwave-safe plate under a loose microwave-safe cover at 50 percent power for 3 minutes, then at full power in 1-minute intervals until both centers reach 165°F, usually another 2 to 4 minutes. Rest for 1 minute before eating.