Preheat your oven to 180°C (350°F) and grease a 12-cup muffin pan.

Chop the bread crusts into small bite-sized pieces and place them in a large mixing bowl.

In a separate bowl, whisk together the eggs, milk, olive oil, zaatar, salt, and pepper until fully combined.

Add the mozzarella cheese, shredded halloumi, and olives (if using) to the bread crusts.

Pour the egg mixture over the bread and cheese mixture.

Stir thoroughly until all the bread pieces are coated with the egg mixture.

Let the mixture sit for 5 minutes so the bread can absorb some of the liquid.

Spoon the mixture evenly into the prepared muffin tin.

Gently press the mixture into each muffin cup so it holds together after baking.

Sprinkle the tops with extra zaatar, sesame seeds, and additional cheese if desired.

Bake for 20–25 minutes or until the tops are golden brown and crisp.

Allow the muffins to cool for 5 minutes before removing them from the muffin pan.

Serve warm or store for later.