Plug in slow cooker and set to high.
Chop potatoes, carrots, and onions. Add to slow cooker.
Add rice to slow cooker and top with chicken stock.
Cook over high for 2 hours (or low for 3 hours).
During the last 15-20 minutes, add pasta to soup and stir to combine.
Lastly, add milk, salt and pepper to pot. Stir to combine. Top with fresh parsley, if desired. Serve hot.