• Prepare the Cassava: Peel cassava and slice into ¼-inch-thick slices. Rinse and drain. To save time, use frozen, pre-peeled cassava; defrost, slice, and rinse.
• In a large pot, bring water and 1 tablespoon of salt to a boil. Add cassava and cook for 20-30 minutes, until fully cooked but still firm. Drain and let cool.
• Make the Milk Mixture:In a bowl or large measuring cup, whisk together eggs, evaporated milk, grated onion, minced garlic, salt, black pepper, green seasoning, and nutmeg (if using).

Assemble the Dish:

• Preheat oven to 350°F.
• Generously butter an 8x10-inch casserole dish. Layer 1/3 of the cassava slices on the bottom of the dish.
• Top with 1/3 of the shredded cheddar and gruyere cheese.
• Pour 1/3 of the milk mixture over the cheese. Sprinkle with thyme leaves and freshly cracked black pepper.
• Repeat the layers two more times (cassava, cheese, milk, thyme, and pepper). Press the cassava layers gently into the milk mixture. Add more milk if needed to ensure it comes close to the top of the cassava.
• Finish with grated Parmesan cheese on top (if using).

Bake:

• Bake uncovered for 45-60 minutes, or until the dish is bubbly, the cheese is golden brown, and your kitchen smells heavenly.
• Serve: Allow to cool slightly before serving. Leftovers taste even better, so feel free to make it a day ahead. You can also assemble the dish the night before, refrigerate, and bake the next day.