Preheat your oven to 375°F (190°C). Use a sharp knife to carefully cut the bagel in half horizontally and then scoop out most of the soft bread from the center, creating a hollow shell.
In a mixing bowl, whisk together the eggs, milk, salt, black pepper, and any optional spices until the mixture is smooth and slightly frothy.
Add the shredded cheese to the egg mixture and gently fold it in, ensuring the cheese is evenly distributed.
Place the hollowed-out bagel shells on a baking sheet lined with aluminum foil or baking paper, cut side up.
Pour the cheese and egg mixture into each bagel half, filling them nearly to the top but leaving a small space to prevent overflow during baking.
Bake in the preheated oven for about 15-20 minutes, or until the filling is puffed, set, and slightly golden on top.
Remove the bagel quiches from the oven and let cool slightly for a few minutes—this helps the custard settle and makes it easier to eat.
Serve warm, perhaps with a sprinkle of additional herbs or spices if desired, and enjoy the creamy, savory inside with the crispy bagel crust.
