Slow Cooker Garlic Buttermilk Mashed Potatoes

Slow Cooker Garlic Buttermilk Mashed Potatoes for nights when dinner needs to be fast, easy and delicious!
Ingredients
3 lbs Yukon Gold potatoes
2-3 cups water
5 garlic cloves peeled and smashed
1 tsp salt
1/2 tsp pepper
4 tbsp butter
1/2-3/4 cup buttermilk
1/2-3/4 cup sour cream
3 green onions sliced (optional)
Instructions