Place the butter on top of the sliced onion. Chop the remaining filling ingredients into bite-sized pieces. Cover with a lid and microwave for 1.5 minutes at 500 W.
While waiting, Combine the egg, milk, salt, and pepper into a bowl and mix together with a whisk.
Once the filling ingredients have finished microwaving, season with salt and pepper.
Pour the egg mixture from Step 2 over the top.
Make sure everything is blended with the mixture.
Scatter the top with the shredded cheese and lightly push into the egg mixture. Cover with the lid and microwave at 500 W for 3 1/2 - 4 1/2 minutes, while keeping an eye on it.
Once it is done, remove this quiche-like dish from the Lekue. Cook it until it reaches your preferred doneness. Since it's a quiche, it's best to cook it until there is no more egg mixture on the bottom.
Since it's basically a quiche, cut it into triangles and enjoy with crusty toast.
If you microwave it completely, it will be a great main dish for your bento.
Story Behind this Recipe
I wondered if I could make this quickly in the morning to use in a bento.
It even tastes great if you use milk instead of heavy cream. The microwaving time in Steps 1 and 6 may vary according to your microwave, so adjust as needed. If you have the time, you could even bake it in the oven in Step 6.