Sauté the Aromatics: Melt the butter in a large skillet over medium heat.
Add the mushrooms and onion, and cook, stirring occasionally, until the mushrooms are deeply browned and tender, about 10 minutes.
Toast the Kasha: While the vegetables cook, combine the dry kasha and beaten egg in a separate medium saucepan.
Stir briskly over low heat until every grain is coated.
Turn the heat to medium and continue stirring constantly until the kasha is toasted, dry, and the grains are separate, about 3-4 minutes.
Combine and Simmer: Add the cooked mushroom and onion mixture to the toasted kasha and toss to combine.
Pour in the hot vegetable stock and salt.
Stir once, bring to a simmer, then cover the pan, and reduce heat to low.
Cook for 10-12 minutes, or until all the liquid is absorbed.
Rest and Fluff: Remove the pan from the heat and let it stand, covered, for 5 minutes. Uncover and fluff gently with a fork before serving.
Don't skip toasting the kasha with the egg. This traditional step coats the grains, preventing them from becoming mushy and ensuring a light, fluffy result.
Finish the dish with a sprinkle of fresh parsley or dill for a burst of freshness that complements the earthy flavors.
