Turn on a multi-functional pressure cooker (such as an Instant Pot®) and select Saute function. Add olive oil, onion, carrots and celery. Cook and stir until vegetables start softening, about 5 minutes. Add beef mince and pork; cook until meat is no longer pink and juices evaporate, about 7 minutes. Pour in wine; cook until liquid evaporates, 10 to 15 minutes. Add passata, tomato puree, salt and pepper.
Close and lock the lid. Set Instant Pot® on Pressure Cook function; select high pressure according to manufacturer's instructions. Set timer for 1 hour. Allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove lid. Add milk; stir until absorbed into the sauce.