Bake cookies for allies using Vex Milk and other ingredients.
Banshee-44 can be found in the Tower Courtyard, and prefers Telemetry Tapioca, which uses Vex Milk and Bullet Spray.
Saint-14 can be found in the Tower Hangar, and prefers Lavender Ribbon Cookies, which use Vex Milk and Personal Touch.
Failsafe can be found on Nessus or in the H.E.L.M., and prefers Infinite Forest Cake, which uses Vex Milk and Impossible Heat.
Nimbus can be found on Neomuna, and prefers Neomun-Pies, which use Vex Milk and Dark Frosting.
Vex Milk can be gathered by defeating Vex combatants.
Additional information about ingredient source and usage can be found by viewing the details screen on Eva's Holiday Oven 2.1.