French toast began as a way to keep stale, leftover bread from going to waste. Today it's less about frugality than putting together a breakfast the whole family will enjoy. The trick is keeping the French toast hot until the rest of your breakfast -- or the rest of your family -- is ready to eat.
Commercial kitchens have large food warmers, climate-controlled boxes that can keep food warm for extended periods. At home, you can use your oven the same way. Preheat the oven to its lowest setting, typically 150 to 175 degrees Fahrenheit. Place the slices in a single layer on a parchment-lined baking sheet as they're cooked. Don't stack them because the ones on the bottom will get flattened. If you have too many slices for one pan, fill a second pan rather than making two layers. Serve breakfast once all the French toast is cooked and the side dishes are ready.
Slow-cookers are an effective way to keep French toast warm until it's time to eat. Preheat the slow-cooker on its lowest setting, usually "warm," and keep it near the stove. As you finish making the slices of French toast, stand them up on their edges in the slow-cooker. Don't layer them horizontally or the bottom ones will get flattened. An oval slow-cooker will hold enough French toast for a family of four. Once filled, move the slow-cooker to the dining area and use it as a serving dish.
Electric Skillet or Griddle
Plug in an electric skillet or griddle and use it to keep French toast warm. Place a wire rack on the cooking surface so the toast keeps warm without scorching on the bottom or overcooking. Set the thermostatic control for 200 degrees Fahrenheit, and cover the skillet or griddle with its lid to retain the heat. If there is no lid, cover it loosely with a sheet of aluminum foil. As you finish cooking each slice of French toast, set it on the rack and replace the cover. Serve once all the French toast is cooked.
Alternative Cooking Method
The above methods assume that you're cooking French toast in the traditional stovetop manner, then keeping it warm until the rest of your breakfast is ready. Another approach is to brown French toast quickly on each side and transfer it to a parchment-lined baking sheet. Finish the toast in your oven for six minutes at 375 degrees Fahrenheit once breakfast is ready. Another option is deep-dish French toast prepared the night before in a casserole dish, then baked in the morning. Once done, it will stay warm until you're ready to serve.