01 - Preheat the 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. Gradually add milk while whisking constantly until sauce thickens. Stir in Gruyère cheese, nutmeg, salt, and pepper. Remove from heat.
03 - Briefly sauté spinach in a skillet until wilted, approximately 2-3 minutes.
04 - Place a puff pastry slice or toasted brioche in the bottom of each ramekin. Layer with sautéed spinach, zucchini slices, tomato, and ham or mushrooms.
05 - Spoon the prepared cheese sauce evenly over the layered vegetables and meat in each ramekin.
06 - Create a shallow well in the center of each ramekin and carefully crack an egg into each well. Lightly season eggs with salt and pepper.
07 - Bake for 20-25 minutes until eggs are just set but yolks remain runny. Adjust cooking time based on preferred egg doneness.
08 - Remove from oven and garnish immediately with fresh chopped chives or parsley before serving.