Mashed Potatoes With Celery Root with milk

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[...]

1/2 lb celery root , peeled and cut into 1-inch chunks 1 large baking potato , peeled and cut in half 1 garlic clove , peeled 2 tablespoons milk 1 tablespoon[...]