Preheat your oven to 180°C (350°F). Lightly grease a 9-inch baking dish and set aside.
Heat olive oil in a skillet over medium heat until shimmering. Add the minced garlic and cook for about 30 seconds until fragrant. Toss in the chopped spinach and a pinch of salt, sautéing for 2-3 minutes until wilted and vibrant green. Remove from heat and let cool slightly.
In a large bowl, whisk together the eggs, milk, salt, pepper, and a pinch of nutmeg or paprika if using. Stir in the shredded cheese until well combined.
Gently fold the sautéed spinach into the egg mixture, ensuring the greens are evenly distributed.
Pour the mixture into the prepared baking dish, spreading it out evenly with a spatula. Smooth the surface for an even bake.
Bake in the preheated oven for 20-25 minutes, until the top is golden brown and the edges are slightly crispy. The center should be set but still slightly jiggly.
Remove from oven and let rest for 5 minutes. This helps the custard settle and makes slicing easier.
Slice into squares or wedges and serve warm, garnished with extra cheese or hot sauce if desired. Enjoy the warm, creamy texture and flavorful greens.