Place the dried macaroni into a large, deep pot, then add 2 1/2 cups of milk along with all the chicken stock and cream. Mix in the mustard powder, garlic powder, onion powder, salt, and white pepper to combine.
Set the pot over medium heat and gently simmer, stirring every so often, until the macaroni is tender but still firm to the bite. If the liquid reduces too quickly before the pasta is cooked, pour in a little more milk to ensure it finishes cooking properly.
Lower the heat to a gentle simmer, then blend in the cream cheese until it smoothly melts. Add the medium cheddar and grated gruyere, stirring until well combined, followed by the shredded mozzarella. If the cheese seems reluctant to melt or the mixture feels overly thick, loosen the sauce with small splashes of milk at a time.
Taste and adjust the seasoning if necessary, then serve your rich, creamy mac and cheese right away and enjoy!
