1Preheat the air fryer to 180°C (350°F).
2In a bowl, whisk together eggs, milk, mustard, salt, and pepper.
3Add bread cubes and mix well to soak. Let sit for 5 minutes.
4Fry bacon in a pan until crispy. Drain on paper towels.
5Fold bacon and half of the grated cheese into the bread mixture.
6Pour the mixture into a dish suitable for the air fryer (greased or silicone).
7Sprinkle remaining cheese on top.
8Cook in the air fryer at 180°C (350°F) for 15–20 minutes, until golden and puffy.
9Let cool for a few minutes, sprinkle green onion if desired, and serve warm.