Make the tamarind paste. If using a wet seedless tamarind block, tear about 1/4 to 1/3 cups' worth into small pieces and add to a medium bowl. Pour in just enough boiling water to cover, and soak 20 to 30 minutes. Once cool enough to handle, squeeze the pulp away from the fibers in the water. Then press through a fine-mesh strainer to remove the fibers. What you have left should resemble an applesauce-type thickness. Measure out 3 tablespoons of the prepared paste.
Prep the proteins. Thinly slice the chicken against the grain. Slice about half of the shrimp into very thin pieces, and leave the rest whole.
Prepare the noodles. Soak or cook the rice noodles according to package directions, then drain.
Heat the griddle. While the noodles cook, preheat the griddle. Set one zone to medium, one to low, and leave one off as a resting area.
Make the sauce. While the noodles are cooking, whisk the tamarind paste, fish sauce, palm sugar, sriracha, and red pepper flakes in a medium bowl until the palm sugar dissolves.
Cook the chicken. Add a little oil to the medium zone and cook the chicken until browned and almost all the way cooked through, about 4 to 5 minutes.
Cook the aromatics. On the low zone, add a small bit of oil to lubricate the cooking surface. Then add the drained noodles. Spread out in an even, thin layer and make a "well" in the center. Cook the shallot, green onion whites, and garlic in the middle of the noodles until fragrant, about 1 minute.
Add the noodles. Toss the fragrant garlic, shallot, and green onion whites with the noodles. When the chicken is almost done, fold into the noodles.
Add the shrimp and sprouts. Add the thinly sliced raw shrimp to a clear area on the griddle to cook about 1-2 minutes. Then toss the chopped dried shrimp (if using) and the thin-sliced shrimp into the noodles. Place the bean sprouts on the griddle to soften slightly. Then toss the bean sprouts with the noodle, shrimp, and chicken mixture.
Cook the whole shrimp. Cook the whole shrimp on the medium zone until pink, 1 to 2 minutes per side. Set the whole shrimp aside for garnishing.
Add the eggs. Pour the beaten eggs onto the low heat side of the griddle. Scramble, chop, and fold into the noodles.
Add the peanuts. Mix about half of the peanuts into the noodles.
Sauce the noodles. Stir the sauce well to redistribute any sugars that sunk to the bottom, then pour it over the noodles. Toss until evenly coated.
Finish. Add the green onion greens and cilantro, if using, and toss for a few seconds.
Serve. Top with the whole shrimp, the remaining peanuts, and chile flakes if desired. Serve with lime wedges.