In 3-quart saucepan, mix milk, salt, pep- per and potatoes, breaking up potatoes with whisk or wooden spoon. Heat to boiling over high heat; reduce heat. Simmer uncovered 4 minutes, stirring frequently with whisk, until thoroughly heated. Remove from heat; stir in 2/3 cup of the cheese.
Top individual servings with remaining 1/3 cup cheese and the bacon; garnish with onions.