Vex Milk is one of the many ingredients you will need to gather up for Dawning 2020 in Destiny 2. The Dawning event is all about baking tasty treats for characters in the game, and you can’t do that without the proper ingredients.
Vex Milk can be gotten by killing Vex enemies anywhere in the game using any method you like. The real trick is finding a decent spot to actually farm this ingredient. Vex Milk also seems to have a lower drop rate than other enemy specific ingredients.
My personal favorite is Bunker E15 at the Eventide Ruins on Europa. This quick Lost Sector is packed with Vex, you can run it quickly, and it also has a very quick reset. It’s been my go-to to gather it up. At the moment, the Eclipsed Zone on Europa is the Asterion Abyss, which has plenty of Vex spawns. You can also work on getting other resources here such as Delicious Explosion from grenade kills and Superb Texture from Super kills, making it a pretty efficient farm.
You can also try Public Events on Nessus as a solid source, but the drop rate of Vex Milk here feels like it is a little nerfed compared to the Lost Sector option.