From The Happy Herbivore
Bring a large pot of water to boil. Add potatoes and cook until fork-tender but not waterlogged, about 8 minutes. Drain potatoes and return to the pot.
Add a splash of plant-based milk and spices, starting with 1 tablespoon garlic and 1 tablespoon onion flakes.
Blend everything together using an electric mixer or potato masher. Add more plant-based milk as necessary to achieve desired consistency. Taste, adding more garlic or onion flakes as desired. Add salt and pepper to taste.