How to Make It
In a nonstick skillet, mix the kasha with the egg whites. Set the skillet over moderate heat and cook, stirring constantly, until the kasha smells toasted and the grains are separate, about 5 minutes.
In a saucepan, heat the oil until shimmering. Add the onions and cook over high heat until tender and browned in spots, 8 minutes. Add the sage and salt and cook for 30 seconds longer. Add the kasha, water and vinegar and bring to a simmer. Cover and cook over low heat until the water has been absorbed, 12 minutes. Add the currants, fluff the kasha with a fork and serve.