Soak Rice Noodles (8 ounce) in warm water for 30 minutes.
Chop the Chicken Breast (8 ounce) if using.
Rinse Bean Sprouts (8 ounce) and Scallion (2 bunch), dice the Garlic (4 clove), cut the Lime (1) into quarters and crush the Dry Roasted Peanuts (1/3 cup).
Drain and cut Firm Tofu (8 ounce) and about 8 stalks of scallion into 1-inch long sticks.
For the sauce, heat a small pot on medium. Mix Tamarind Concentrate (1/4 cup), Palm Sugar (4 ounce), Fish Sauce (1/4 cup), Water (1/4 cup) and Ground Chili Pepper (1 teaspoon). Stir and crush palm sugar until fully dissolved and turn off heat.
When noodles are soft enough (but still slightly harder than al dente pasta), rinse them in cold water and drain. Make sure all of your ingredients are set up and divided into equal portions. You`ll be cooking one portion at a time.
Add 2 tbsp of oil to a wok or large non-stick pan. Heat on medium-high, until very hot. Add chicken breast (8 oz), if you are using it and cook for 1 min.
Add firm tofu and garlic. Cook for about 45 secs, stirring frequently. Garlic should now be brown.
Stir in noodles, then add 3 tbsp of sauce mixture. Coat noodles and meat well and stir vigorously to keep noodles from sticking. After about 2 mins, taste noodles to check if they’re soft enough.
If not, add 2-3 tbsp. of water and continue to cook for a little longer.
Add Shrimp (8 ounce) and combine with noodles. Push everything aside creating an empty space in the middle.
Crack the Egg (4) wait 15 secs to set, then mix into the noodles. Sprinkle some Ground White Pepper (1 teaspoon), add bean sprouts, and up to 1 tbsp more sauce.
Stir everything for 1 minute, then add scallions.
Turn off heat and toss. To serve, top with crushed peanuts, dried onions and a generous squeeze of lime juice.