These are, essentially, savory bread puddings: bread is layered with cheese and meat or vegetables then soaked in a milk and egg mixture. They are wonderful for early morning occasions, like Christmas, because they are entirely assembled the day before, then refrigerated overnight so the strata absorbs the custard. All that’s required the next morning is simply to pop them into the oven for an hour or so, let them rest a few minutes, and serve, leaving you free to stuff stockings, preside over gift giving or brew coffee.