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

Slice the zucchini: Cut into thin half-moons, about 1/4 inch thick. Even slices help it cook evenly.

Draw out moisture: Toss zucchini with 1 teaspoon salt and spread it on a towel-lined baking sheet. Let it rest 15–20 minutes. Pat dry thoroughly. This step keeps the casserole from getting watery.

Sauté aromatics: Warm olive oil or butter in a large skillet over medium heat. Add onion (if using) and cook 3–4 minutes until soft. Stir in garlic for 30 seconds until fragrant.

Par-cook the zucchini: Add the zucchini to the skillet. Cook 4–5 minutes, stirring occasionally, just until it starts to soften. Season with pepper and a pinch more salt if needed. Remove from heat.

Make the creamy base: In a bowl, whisk heavy cream, cream cheese (softened helps), and eggs until smooth. Stir in half of the shredded cheeses and the herbs. Add red pepper flakes if you like a little heat.

Combine: Fold the sautéed zucchini into the creamy mixture. Taste and adjust salt and pepper.

Assemble the casserole: Spread the mixture in the prepared baking dish. Top with the remaining shredded cheeses and the Parmesan. If using, sprinkle pork rind crumbs or almond flour over the top for crunch.

Bake: Bake uncovered for 20–25 minutes, or until the casserole is set at the center and the top is golden and bubbly.

Rest and serve: Let it rest 10 minutes before serving. This allows the sauce to thicken and gives clean slices.