Wash and peel your potatoes, then cut them into cubes about 1 square inch in size.
Place the potato cubes in the pot of cold water as soon as you cut them. (This prevents the air from getting to the potatoes so they won't oxidize and turn brown. You can leave them in this water for a few hours while you prep any other food and cook them about 30 minutes before you want to eat so they are fresh and warm.)
Add salt to the cooking water and bring the potatoes to a boil.
Adjust the heat so that they stay at a rolling boil for about 15-20 minutes until the potatoes break easily when pierced with a fork. (Cooking time will depend on the size of your cubes and altitude.)
Pour off the cooking water and immediately add 3/4 cup plant milk, 4 tablespoons vegan butter, and 1/2 teaspoon garlic powder to the hot potatoes. (You can do this in a mixing bowl or in the pot you cooked them in.)
Mash with a hand potato masher until the desired consistency is reached and add salt and pepper to taste. You may need to add another splash of milk to them if they seem dry or you want fluffier potatoes.
Notes
The smaller that you cut the potatoes, the faster they will cook. You can save some work and cut them into larger pieces, but you will need to let them boil for an extra 5 minutes or more.
Be sure to put plenty of salt in the cooking water. This will cook into your potatoes and give them a better flavor than simply adding salt at the end. (Most of this salt will be poured off with the cooking water so don't get worried about them being too salty.)
Cover the potatoes with enough water to cover them, but be sure to leave room for the water to rise when it boils. It will form a foam on the top when boiling that can be scooped off with a large spoon if it looks like it may boil over.
Don't use an electric mixer or over mash the potatoes. When they are over mashed they become sticky and have a glue-like texture.
This recipe uses 1/2 of a 5 lbs bag of potatoes. It will serve 6 as a side dish, if you are making this for a crowd, you will want to double the recipe.