Start making the soffritto by finely chopping the onion, carrot and celery or if you don't want chunks in the sauce, you can use a mixer until they're finely shredded.
Add 2-3 tablespoon of EVO oil in a large pot and add the soffritto. Turn on the medium heat and cook until they become really soft (do not brown).
Add the ground meat and the sausages and turn the heat to high and cook until the meat changes color, then add salt and pepper to season the meat. Finally pour the wine and let evaporate the alcohol.
Purèe the San Marzano tomatoes in a blender, then turn the heat to low and add the pureed tomatoes to the pot. Add enough beef stock to cover all. Add also the concetrated tomato paste and mix.
Taste and season accordingly; if necessary, add some sugar to break the acidity of the tomatoes.
Finally, add the bay leaves and the juniper berrier. Mix well with a wooden spoon and cover the pot with the lid. Let it simmer for at least 2 hours stirring every once in a while. If the sauce reduces too much, add some more beef stock.
Notes
You can add ⅓ cup of milk 15 minutes before the cooking time ends to add more creaminess, break the acidity of the tomatoes and make the flavors more delicate.You can let the sauce cool and then pour it into freezer bags or freezer containers and freeze for up to 2 months.You can save time by prepping and freezing the Soffritto (mix of onions, carrots and celery) in small portions. See this post about Soffritto (Mirepoix) for the details.