– 3 tablespoon salted butter – 1 large white onion, diced – 1 pound potato, [0.45 kilo], Yukon – 1½ quart chicken stock, [1.5 liters], – 1 large head broccoli, [0.45 kilo], cut into florets – 2 cups whole milk – 1½ teaspoons salt, or to taste, divided – 1 teaspoon black pepper – 1 bunch flat parsley – ½ cup cream cheese – 1 cup grated mozzarella cheese or white cheddar – ¼ cup freshly-grated Parmesan