Heat the oil in a large heavy based saucepan, add the onions, and cook on a medium heat, stirring frequently, for 5 minutes or until soft. Add the beef and cook, stirring frequently, for another 5 minutes or until no longer pink. Add the garlic and cook for another minute, then pour in the wine and allow to simmer and reduce for 5 minutes.
Add the tomatoes, bay leaves, and thyme, bring to a boil, then reduce the heat and simmer for 30 minutes, stirring occasionally. Taste and season with sea salt and freshly ground black pepper.
Let cool completely, then remove and discard the bay leaves. Divide the ragù evenly among 4 freezer bags (2 portions per bag), seal, and freeze for up to 6 months.
To serve, defrost in the refrigerator overnight, then transfer to a saucepan and heat until piping hot. Serve with pasta or creamy mashed potatoes.