Carefully carry the pan over to the oven (have the door already open) and place on the centre rack. Bake until the eggs are set, the temperature on an instant read thermometer should read 160F. This can take anywhere between 18-25 minutes depending on your oven. You can also do this by placing the baking sheet on the rack before filling.
Slice the eggs into 6 even squares, for 6 sandwiches. If you are only going to eat one or two right then and there, feel free to slice the remaining eggs into smaller slices for mid-week breakfast or lunch prep.
Toast the bread, butter it if desired, and place an egg square on one slice. Add a few dashes of hot sauce if this appeals to you. Lay a small handful of arugula on top. Top with the other buttered toast slice.
Feel free to add more cheese, bacon, tomato etc, see Notes
Feel free to use your favourite grated cheese, whether Cheddar, Gouda, Jarlsberg, or even a Tex-Mex Blend!
You can use arugula or lettuce in the sammie, or forego anything green if you feel like it. You can add extra cheese, sliced bacon or tomato etc.
You can use a 11 x 17 pan (or thereabouts) by upping the eggs to 18 and the milk to 1/2 cup. This will easily feed 8-10 people. Make sure which ever pan you use, that the edges are at least 1 inch high.
Serve as part of a brunch spread, or use in meal prep during the week.