Directions

1. Preheat oven to 425°F. Toss together mushrooms, oil, thyme sprigs, 1 teaspoon of the salt, and 1/4 teaspoon of the pepper on a large rimmed baking sheet. Roast in preheated oven, stirring occasionally, until browned, about 25 minutes. Remove from oven; discard thyme sprigs, and set mushroom mixture aside.
2. While mushrooms roast, stir together groats and egg white in a small bowl until groats are evenly coated. Heat a medium saucepan over medium-low. Add groat mixture, and cook, stirring constantly, until groats are toasted and dried all the way through, about 3 minutes. Add water and 1/2 teaspoon of the salt. Bring to a boil over medium-high; reduce heat to medium-low, and simmer, covered and undisturbed, until liquid is absorbed and groats are tender, 10 to 12 minutes. Set aside.
3. Heat 1/4 cup of the schmaltz (or butter) in a large deep-sided skillet over medium. Add onions and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper; cook, stirring often, until mixture is very soft and browned, about 20 minutes, adding more water, 2 tablespoons at a time, as needed to deglaze and prevent browned bits from burning.
4. Meanwhile, bring a large pot of salted water to a boil over high. Add pasta; cook according to package directions for al dente, about 10 minutes. Drain, reserving 2 cups cooking water.
5. Add cooked pasta, roasted mushrooms, 1 cup reserved cooking liquid, and remaining 1/4 cup schmaltz to onion mixture in skillet. Cook over medium, stirring constantly, until liquid thickens to a saucy consistency and coats pasta, about 3 minutes, adding up to remaining 1 cup cooking water, as needed, to achieve desired sauce consistency. Remove from heat, and stir in cooked groats. Season with additional salt and black pepper to taste. Divide mixture evenly among 6 bowls. Garnish with chives and additional thyme leaves. Serve.