Mashed Potatoes with butter

3 lbs yukon gold potatoes , peeled and cut into 2-inch pieces 1 lb celery root , peeled and cut into 2-inch pieces 2 garlic cloves , sliced 1 cup light cream[...]

2 lbs yukon gold potatoes or 2 lbs russet potatoes , peeled,cubed 1 cup sweet potato , peeled,diced (yellow variety) 1/2 cup rutabaga, peeled,diced 1/2 cup[...]