1Place Reynolds™ Slow Cooker Liners inside a 5- to 6 1/2 -qt slow cooker bowl. Make sure that liner fits snugly against the bottom and sides of bowl and pull the top of the liner over rim of bowl.
2In cooker, mix boiling water, milk, butter, sour cream and cream cheese with whisk until blended. Add garlic salt, pepper and dry potatoes; mix just until blended.
3Cover; cook on Low heat setting 1 hour 30 minutes, stirring once after 1 hour.
4Before serving, stir potatoes. Serve immediately, or hold in slow cooker on Low heat setting up to 3 hours, stirring every 30 minutes. If potatoes become too thick, stir in additional milk, about 2 tablespoons at a time. Serve with gravy or sprinkle with chopped parsley.