Whisk milk, eggs, salt, and several grinds of pepper until smooth.

Spread half the torn bread in a 13- by 9-inch pan.

Pour in half the egg mixture and then sprinkle half the cheese and scallions over the bread.

Make another layer with remaining bread, egg mixture, cheese, and scallions

Let stand, occasionally pressing on bread, until it has absorbed the milk mixture, at least 15 minutes, but way better if you have time to refrigerate it overnight.

Adjust oven rack to middle position and heat oven to 325 degrees. Bake until custard is set and strata is golden brown and puffy, 50 minutes to 1 hour.

Remove from oven, let stand for 8 to 10 minutes, and then serve immediately.

For even better strata, cool completely—you can even refrigerate or freeze it. Shortly before serving, halve the strata, crosswise, removing each block of the custardy bread from the pan.

Cut each half into 8 squares.

Place strata squares on a greased rimmed baking sheet and bake until crisp and deep golden brown, about 20 minutes longer.