01 - Preheat oven to 375°F. Lightly grease four individual ramekins or a medium baking dish.
02 - Melt butter in a saucepan over medium heat. Whisk in flour and cook for 1 minute. Slowly add milk, whisking constantly until thickened. Stir in Gruyère cheese, nutmeg, salt, and pepper. Remove from heat.
03 - Briefly sauté spinach in a skillet until wilted.
04 - Place puff pastry or toasted brioche in bottom of each ramekin. Layer with sautéed spinach, zucchini slices, tomato, and ham (or mushrooms).
05 - Spoon cheese sauce over layered vegetables and ham.
06 - Make shallow well in each and crack an egg on top. Season eggs lightly with salt and pepper.
07 - Bake for 20-25 minutes until eggs are just set but yolks remain runny. Adjust time for preferred doneness.
08 - Garnish with fresh chives or parsley before serving.