01 - Preheat the oven to 375°F. Lightly grease four individual ramekins or a medium baking dish with cooking spray or butter.
02 - Melt butter in a saucepan over medium heat. Whisk in flour and cook for 1 minute to form a roux. Gradually whisk in milk, stirring constantly until the sauce thickens and smooths. Remove from heat, stir in Gruyère cheese, nutmeg, salt, and pepper until melted and combined.
03 - Heat a skillet over medium-high heat. Add spinach and sauté briefly until just wilted, about 2 minutes. Remove from heat.
04 - Place a slice of puff pastry or toasted brioche in the bottom of each ramekin. Layer with sautéed spinach, zucchini slices, tomato, and ham or mushrooms.
05 - Spoon cheese sauce evenly over the layered vegetables and ham. Make a shallow well in the center of each ramekin using the back of a spoon.
06 - Carefully crack one egg into each well. Season eggs lightly with salt and pepper.
07 - Bake for 20–25 minutes until egg whites are fully set but yolks remain slightly runny. Adjust baking time by 2–3 minutes longer for firmer yolks.
08 - Remove from oven and let rest for 2 minutes. Sprinkle with fresh chives or parsley and serve immediately.