Heat half of the oil in a large skillet. Add the groats and stir quickly to coat them with the oil. Toast over medium heat, stirring frequently, until they turn darker and aromatic. Pour the broth over the groats and bring to a simmer.
Simmer gently until the water is absorbed, about 15 to 25 minutes, depending on the grind of the groats.
Cook the noodles separately until just al dente, then immediately rinse with cool water.
Heat the remaining oil in a large skillet or stir-fry pan. Add the leeks and sauté over medium-low heat for 5 minutes, or until limp. Add the bell pepper, jicama or turnip, and cabbage. Turn up the heat to medium-high and stir-fry until tender-crisp.
Add the cooked groats and vermicelli along with the remaining ingredients and stir together gently. Cook over low heat, stirring frequently, for 3 to 4 minutes, until everything is piping hot. If the mixture seems dry, add just a bit more broth or water. Serve at once.