01 - Preheat the oven to 375°F. Prepare four individual ramekins or a medium baking dish by greasing lightly.
02 - In a saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Slowly add milk, whisking constantly until thickened. Stir in Gruyère cheese, a pinch of nutmeg, salt, and pepper. Remove from heat.
03 - Briefly sauté spinach in a skillet until wilted.
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 over the layered vegetables and ham.
06 - Make a 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 baking time for preferred doneness.
08 - Garnish with fresh chives or parsley before serving.