Heat olive oil in a large skillet over medium-high heat.
Add beef tips in batches and brown on all sides, about 3-4 minutes per batch. Remove browned beef tips and set aside.
In the same skillet, add sliced onion and cook until softened, about 5 minutes.
Add sliced mushrooms and cook until they release their moisture and begin to brown, about 7 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Return beef tips to the skillet and stir to combine.
Pour in beef broth and water, then add dried thyme, dried parsley, salt, and black pepper. Stir well.
Bring mixture to a simmer, then reduce heat to low, cover, and cook for 30 minutes until beef is tender.
In a small bowl, whisk together cornstarch and cold water until smooth.
Slowly stir cornstarch mixture into the skillet and cook for 3-5 minutes until gravy thickens.
Remove from heat and allow to cool completely before transferring to freezer-safe containers or bags.
Label and freeze for up to 3 months.
To reheat, thaw overnight in the refrigerator and warm on the stovetop over medium heat until heated through.