Yes, you can reheat leftover French Toast in a microwave oven. Here's a simple method to do it:
Place the French Toast on a microwave-safe plate. Arrange the slices in a single layer, without overlapping them.
If your microwave has a turntable, make sure it's functioning properly. If not, you may need to rotate the plate manually during the cooking process to ensure even heating.
Cover the French Toast with a microwave-safe cover or microwave-safe plastic wrap. This helps to trap the moisture and prevent the French Toast from drying out.
Set the microwave to medium power or around 50% power level. Cooking at a lower power level will help to heat the French Toast more evenly without making it overly tough or chewy.
Start with a short cooking time, such as 30 seconds, and then check the French Toast. If it needs more heating, continue to microwave in 10 to 15-second intervals until it reaches your desired level of warmth.
Remove the plate from the microwave oven carefully, as it may be hot. Let the French Toast sit for a minute or two before serving to allow the heat to distribute evenly and to avoid burning yourself.
Remember that reheating in the microwave may not result in the same level of crispness as when it was freshly made. If you desire a crispier texture, you could consider toasting the French Toast in a toaster oven or on a stovetop in a non-stick pan with a bit of butter.