Spinach-gruyere strata is a lot like lasagna–it has a lot of parts that have to be prepared, put together, then baked. This is a recipe where you don’t want to substitute something else for the Gruyere cheese, use onions instead of shallots, or leave out the wine. The amazing flavor is worth going out of your way to buy ingredients that you might not otherwise use.
thaw and drain frozen spinach
Plan ahead for this step. It does take a while to dry the frozen spinach enough so the strata doesn’t come out runny. You can either thaw the spinach in the microwave or just leave it out for most of a day at room temperature. Put the spinach in a large strainer over an empty bowl. Use the back of a large spoon to press out the extra liquid.
press the spinach-gruyere strata with weights
Once you’ve put the strata together, cover it tightly with plastic wrap. Place another baking dish on top of the plastic. I use large cans of tomatoes to press the baking dish into the strata. It really makes a difference to make sure the top layer of bread is completely saturated with the custard. Otherwise, the top bread pieces stay too dry and crusty. You want the top to be moist enough it just makes a light crust on the top with the cheese.
double or triple the recipe for a crowd
This recipe can easily be doubled or tripled for a large crowd. For a double recipe, use a 9 x 13 baking dish. For a triple recipe, use an 11 x 17 baking dish. Remember to add more time for baking larger batches.