Peel and cut the potatoes into small chunks. In a large soup pot, add the potatoes and add water just until they are covered. Bring to a boil over high heat.
Boil for about 5 minutes then stir in the onion. Continue to boil just until the potatoes become slightly tender (about 5 more minutes). Be careful not to over boil the potatoes so they don’t turn mushy.
Drain the water from the potatoes. Stir in the butter and milk, and the seasonings. Bring back to a boil.
Reduce to a simmer and stir in the Velveeta. Continue cooking, about 10 minutes, until the cheese melts and is smooth, stirring frequently. Serve warm.