Put potatoes & garlic into a large saucepan, add enough water to just cover & bring water to a boil; reduce heat to medium low & simmer, covered, 20 - 25 minutes until potatoes & garlic are very tender.
Drain well, return to saucepan & put over low heat for a minute or so to dry out potatoes, shaking the saucepan so they don't stick.
Combine milk & butter in a microwave-safe bowl & nuke on high for 1 - 2 minutes until milk is steaming & butter starts to melt; stir milk mixture, cheese & seasonings into potatoes.
Squeeze potatoes through a ricer OR mash roughly with a fork, then beat until smooth with an electric mixer, being careful not to overdo it or they will become gluey.
Spoon into a warm serving dish; sprinkle with parsley & serve immediately.