1. Prepare shrimp by combining the garlic, sesame/chili oil, vinegar, sugar, lime juice, salt, and black pepper; coat the shrimp. Set aside. This may also be prepared ahead of time and kept covered in the refrigerator.
2. Boil water and cook noodles for about five minutes, or according to package instructions, then drain.
3. Make the sauce: Over low heat, dissolve sugar in the water, stirring frequently. Remove from heat and wait five minutes. Add lime juice, chili pepper, and fish sauce and vinegar. Return the saucepan to very low heat.
4. Cook shrimp: Heat vegetable oil in a skillet on medium heat. Turn to high heat and add shrimp, sautéing about 3 minutes or until cooked through.
5. Taste the sauce and adjust seasonings as desired. Carefully toss together noodles, shiitake mushrooms, and cucumbers with half the sauce, then transfer to a platter. Sprinkle cilantro and mint over all. Add shrimp last.
6. Garnish the platter with lime wedges and sprigs of mint and cilantro. Pour the rest of the sauce in a small bowl so people can help themselves to more.Serving Size: 1 bowl of noodles and shrimp