6 tablespoons oyster sauce
Freshly ground pepper
3 pounds boneless sirloin steak (about 1 1/2 inches thick)
Olive oil, for the pan
2 tablespoon packed brown sugar
2 bunch scallions, white and green parts separated, cut into 1 1/2-inch pieces
Toasted sesame oil, for drizzling
Roughly chop the radish greens. Cut the radishes into eighths.
5 cups beef broth
2.) Meanwhile, bring the remaining 5 tablespoons teriyaki sauce, 2 tablespoon oyster sauce and 4 teaspoons ginger, the vinegar, brown sugar and 5 cups beef broth to a simmer in a saucepan, stirring to dissolve the sugar. Add the sweet potatoes, radish wedges and scallion whites and cook, covered, stirring occasionally, until just tender, about 10 minutes.
3.) Add the chanterelles, radish, and scallion greens and cook until crisp-tender, about 5 minutes. Divide the vegetables, broth and steak among shallow bowls. Drizzle with sesame oil and add cooked udon noodles if desired.