Basic mashed potatoes

4 lb Yukon gold potatoes
3 cups of cold water
1 teaspoon seal salt
1 cup of cooking liquid
1 cup warm 2% milk
1/4 cup unsalted butter
1/2 cup reserved cooking liquid
Pepper for taste

For the Bacon-onion mashed potatoes:
Basic mashed potatoe recipe (see above)
8 chopped, cooked slices bacon
1/4 cup cup finely chopped scallion greens

For the Garlic mashed potatoes:

1 head garlic
Cloves
1 cup warm 2% milk