The spring rolls. In a large pot, heat the oil and add the onion. Cook for about 8 minutes, until golden and crisp. Add the meat and add enough water to cover it. Bring back to a boil, reduce the heat, and cook for 25-30 minutes. Add the chile powder, sugar, 1 teaspoon salt, and white vinegar. Cook for a few minutes more, or until the meat is cooked through. Remove the meat from the pot and slice crosswise. Leave the broth in the pot - we will need it to cook shrimp.
Clean the shrimp by cutting off the heads, removing the shells and tails, and deveining them. Bring the broth to a boil, add the remaining ½ teaspoons salt, and cook the shrimp for a few minutes, until done. Transfer the shrimp to a plate and <g class="gr_ gr_93 gr-alert gr_spell gr_run_anim ContextualSpelling" id="93" data-gr-id="93">halve</g> lengthwise.
Cut the cucumber and carrot into matchsticks matching the size of your rice paper rounds.
Fill a large bowl with warm water. Dip one rice paper round in the water for a few seconds (not for too long or it will become too soft) and place it on a flat surface. Starting about 1 ½ inch (4cm) from the bottom edge of the disk, arrange the shrimp, then top with the lettuce, pork, mint, basil, rice noodles, cucumber, and carrot. Don't overstuff the rolls! Fold the sides over the filling and fold up the bottom, rolling away from you. Repeat with all the remaining ingredients.
The peanut sauce. In a bowl, mix together all the ingredients until smooth.
Serve the spring rolls with the peanut sauce and enjoy!