Make the spicy peanut sauce: In a blender or food processor, combine the peanuts, garlic, shallot, chili pepper (if using), sweet soy sauce, tamarind paste and water. Blend until smooth.
Transfer the mixture to a small saucepan. Bring to a boil over medium heat, stirring constantly (be careful not to burn the sauce here). Quickly reduce heat to low and simmer for 5-10 minutes, until the sauce has thickened.
Season the sauce with salt and sugar, to taste. Set aside to cool. To make the consistency more like a salad dressing, simply mix in a little water.
Boil the vegetables until they are tender but still crisp, about 5-7 minutes. Drain and set aside to cool.
Assemble the salad: On a large serving platter, arrange the cooked vegetables, boiled eggs, and tofu/tempeh.
Drizzle the peanut sauce over the top of the salad, or serve it on the side as a dipping sauce.
Serve the Gado Gado salad immediately, garnished with additional chopped peanuts and fresh herbs, if desired. Enjoy!