Set Instant Pot to SAUTÉ and add a good glug of oil. Add chopped vegetables, bay leaves, mixed herbs and season with 1 tsp of salt and some freshly ground pepper. Fry stirring frequently for approximately 15 minutes until vegetables are soft.
Add chopped/minced pancetta/bacon and beef mince and fry breaking it up and stirring frequently for another 15 minutes. The meat will release some liquid as it cooks which is to be expected. Keep frying until it's almost evaporated.
Add good splash of red wine (if using) and fry some more until it evaporated and meat mixture starts to sizzle.
Press Keep Warm/Cancel Button to cancel SAUTÉ function.
Add chopped tomatoes. Fill each tin half way with water, swirl around and add it to the pot. Add 1 tsp of sea salt, some more freshly ground pepper and 2 parmesan rinds (if using). Stir well.
Put on the lid and lock it in place making sure that the black, steam releasing valve is pointing to "Sealing". Set your Instant Pot to "Meat/Stew" setting on High Pressure, setting adjusted to More for 15 minutes.
When the time is up turn the pot off by pressing Keep Warm/Cancel button and let the pressure go down naturally (NPR - Natural Pressure Release). It will take approx. 20-25 minutes.
Open the lid, add milk and stir well. Press SAUTÉ button yet again and let the ragù reduce slightly for approx 10min until it reaches desired consistency.
Check seasoning and add some salt/pepper if required.
Serve over pasta and topped with lots of grated parmesan.