Preheat your oven to 180°C (350°F) and lightly grease your baking dish or ramekins.
In a skillet over medium heat, add a splash of oil and sauté the spinach until wilted and tender, about 2-3 minutes. If using, add the minced garlic during the last minute to release its aroma. Remove from heat and let cool slightly.
In a mixing bowl, crack the eggs and whisk vigorously until the mixture is frothy and well combined. Add the milk or cream, a pinch of salt and pepper, and the optional nutmeg. Whisk again until smooth.
Chop or shred your cheese and fold half into the egg mixture, ensuring an even distribution for a cheesy, gooey texture.
Gently squeeze excess moisture out of the cooked spinach to prevent sogginess, then fold the spinach into the egg mixture carefully, ensuring even coverage.
Pour the entire mixture into your prepared baking dish or ramekins, spreading it out evenly. Top with the remaining cheese for a golden, bubbly crust.
Place the dish in the oven and bake for 25-30 minutes, or until the top is golden brown and the edges are slightly puffed. The bake should be set in the center but still slightly jiggly.
Once done, remove from the oven and let rest for 5 minutes. This helps the custard set and makes slicing easier.
Slice into portions and serve warm, garnished with fresh herbs if desired. Enjoy the tender, custardy texture with a lightly crispy top.
