In a large pot of lightly salted boiling water, cook the udon noodles for about five minutes or until tender.
Drain and rinse the noodles under cold running water and let cool.
Whisk the peanut butter, milk, ginger, garlic, vinegar, soy sauce, sesame oil, and red pepper flakes in a small bowl until well blended.
In a large salad bowl, combine the cooked noodles, cucumber, sprouts, carrot, green onions and mint. Wisk the peanut butter dressing and pour it over the salad. Stir until well coated and serve chilled on a bed of romaine leaves.
