In a medium saucepan, combine the kasha and beaten egg.
Stir constantly over medium heat for about 3 minutes, until the egg coats each grain and the mixture looks dry and smells toasty. 2. Make a well in the center of the kasha, add the 1 tablespoon (15 ml / 0.5 fl oz) of butter, and allow it to melt.
Stir to combine, then pour in the hot vegetable stock and salt. 3.
Bring the mixture to a boil, then immediately reduce the heat to a low simmer.
Cover the saucepan and cook for about 10-12 minutes, or until all the stock has been absorbed.
Remove from heat and let it stand, covered. 4.
While the kasha cooks, prepare the sauce. Melt 3 tablespoons (45 ml / 1.5 fl oz) of butter in a large skillet over medium-high heat.
Add the diced onion and sauté for 3-4 minutes until softened and translucent. 5.
Add the sliced mushrooms, thyme, cayenne, and a generous amount of freshly ground black pepper to the skillet.
Cook, stirring occasionally, for about 10 minutes, until the mushrooms have released their liquid and started to brown nicely. 6.
Reduce the heat to low and stir in the sour cream.
Cook gently for 2 more minutes until the sauce is heated through and bubbly, but do not let it boil. 7. To serve, fluff the cooked kasha with a fork. Spoon a generous portion onto each plate and top with the creamy mushroom sauce.
Garnish with fresh parsley and serve immediately.
Don't skip toasting the kasha with the egg. This traditional step is key to preventing a mushy texture and ensures each grain remains separate and fluffy.