Prep the zucchini: Trim the ends. Use a mandoline or vegetable peeler to make thin ribbons, or a spiralizer for zoodles. Lay them on paper towels, sprinkle lightly with salt, and let sit 10–15 minutes to draw out moisture.

Preheat the oven: Set to 375°F (190°C). Grease a 9x13-inch baking dish or similar casserole.

Blot and sauté: Pat the zucchini dry well. Heat olive oil in a large skillet over medium-high. Sauté zucchini in batches for 2–3 minutes just to soften and release more water. Transfer to a colander to drain.

Make the Alfredo sauce: In the same skillet, lower heat to medium. Melt butter and add garlic. Cook 30–60 seconds until fragrant. Stir in cream and bring to a gentle simmer.

Enrich the sauce: Whisk in cream cheese until smooth. Add Parmesan, a pinch of nutmeg, salt, and pepper. Simmer 2–3 minutes until slightly thickened. If using egg yolk, temper it by whisking a spoonful of hot sauce into the yolk, then whisk the mixture back into the pan. Do not boil.

Taste and adjust: Add more salt, pepper, or Italian seasoning if you like. The sauce should be bold and a touch garlicky.

Assemble the bake: Add the drained zucchini to the sauce and toss gently to coat. Transfer everything to the prepared baking dish. Sprinkle mozzarella and a little extra Parmesan over the top.

Bake: Place in the oven for 15–20 minutes until the top is melted and bubbling. For a deeper golden top, broil for 1–2 minutes at the end.

Rest and serve: Let it sit 5–10 minutes so the sauce settles. Garnish with fresh parsley and serve warm.