Matzoh brei is not much more than scrambled eggs with broken up pieces of matzoh, and it's one the simplest and most delicious ways to use up leftover matzoh ever.
Melt the butter in a large skillet over medium heat. Add the onions, season with salt and pepper and saute for about 4 minutes, until softened.
Meanwhile break the matzohs into pieces about 1-inch in size and place them in a bowl. Have a strainer ready. Fill the bowl with hot water so that the matzoh is covered. Let sit for 30 second, then drain the matzoh in a strainer.
Beat the eggs in the same bowl and season with salt and pepper. Add the matzoh and stir to combine. Transfer the egg and matzoh mixture to the pan with the onions and cook, stirring occasionally, until the eggs are as firmly cooked as you like them, breaking up the mixture (or let it cook until the bottom is firm and browned and use a spatula to flip the mixture as a single entity, then allow the scone side to brown). Transfer to a plate and serve hot.
Notes
Ratio of Eggs to Matzoh for Matzoh Brei
The ratio of matzoh to eggs differs radically from recipe to recipe. Some people use 1 sheet of matzoh per egg, resulting in a very matzoh sense matzoh brei. I’ve eaten and made it in many ways, and I like the 2 eggs to every sheet of matzoh ratio. You can play with it and decide for yourself. The good news is that you can’t mess it up, you’ll only have varying consistencies as a result of changing up the matzoh to egg proportion.