Ultra Creamy One Pot Mac and Cheese

Name: Ultra Creamy One Pot Mac and Cheese
Prep time: 5 min
Cook time: 20 min
Total time: 25 min
Cuisine: American
Ingredients: 1lb / 500g Dried Macaroni; 2 1/2 - 3 cups / 600 - 720ml Milk, (at room temp, or as needed (I use semi-skimmed)); 2 cups / 480ml Chicken Stock ((not piping hot)); 1 cup / 240ml Heavy/Double Cream, (at room temp); 1 tsp Salt; 1/2 tsp Mustard Powder; 1/4 tsp EACH: Onion Powder, Garlic Powder, White Pepper; 4oz / 125g Cream Cheese, (leave at room temp); 2 1/2 cups / 250g Medium Cheddar ((see notes)); 1 cup / 100g Gruyere, (grated); 1/2 cup / 50g Mozzarella, (shredded)