Prepare the Dressing: In a saucepan over medium heat, combine broth, soy sauce, sugar, and vinegar, stirring until the sugar dissolves, about 2-3 minutes. In a small bowl, mix cornstarch with cold water and whisk it into the hot mixture. Continue cooking for another 1-2 minutes until the dressing thickens slightly; remove from heat and allow it to cool.

Cook Protein: Bring a pot of water to a rolling boil, adding your choice of chicken, beef, or tofu to blanch. Cook for about 3-5 minutes, removing when done and slicing thinly against the grain.

Cook Noodles: In the same boiling water, add the rice noodles and cook according to package instructions, usually around 4-6 minutes until tender but chewy. Drain and rinse under cold water to stop cooking and reduce stickiness.

Chop Vegetables and Herbs: While cooling, chop fresh vegetables and herbs, rinsing and drying the lettuce and slicing into bite-sized pieces.

Assemble Salad: In a large bowl, combine the cooked noodles with the cooled dressing, tossing thoroughly. Add sliced protein, vegetables, and herbs, mixing gently.

Top and Serve: Transfer the salad to individual serving bowls or a platter. Garnish with crushed peanuts, fried shallots, or jalapeños for an extra touch. Serve immediately.