In a medium skillet, heat about 1 ½ Tbsp butter or oil and begin frying onions. It's ok to let them brown in places. After a few minutes season with salt and pepper, and add mushrooms. Let this continue to cook for 5-10 more minutes, until brown and fragrant. Add kimchi and remove from heat.
Crack and whisk eggs in a medium bowl, adding a pinch of salt and pepper.
Fill a larger bowl with cold water, and set a colander next to it. Break matzos in half and submerge in water for ~15-20 seconds, then remove to colander. Work in batches if necessary.
In a larger skillet, heat about 3 Tbsp butter or oil. When bubbling, add matzos, breaking up pieces with a spoon or spatula. When it starts to brown in places, add a few good squeezes of Bobbie's Boat Sauce, allowing it to further moisten the matzoh and caramelize with the heat of the pan.
Add mushroom mixture. Without too much prodding, saute gently for a few minutes until thoroughly hot, then add the egg mixture, while lowering the heat.
Cook matzo brei for another 2-3 minutes, stirring judiciously and letting the egg firm up on its own.
Serve with sour cream, chives, and more Bobbie's Boat Sauce!