How to make Vietnamese bun?
I have the same addiction and live in a place where the closest Vietnamese restaurant is over 30 miles away. For this reason, I have accumulated several cookbooks on Vietnamese cooking, but the one that I use the most often is called "Easy Vietnamese Home Cooking for Everyone" (you can order it from Amazon). It's a great little paperback with an ingredient section in the front with photos - a quick and easy reference guide. (I also have the book "Asian Ingredients" by Bruce Cost which is far more detailed, but for day to day cooking, I just love this little paperback). The recipes are simple and directions are accompanied by step-by-step photos.
Bun dishes are easy to make and incredibly delicious. But given their freshness and simplicity, quality ingredients are required. Herbs must be crisp, meats must be high-quality and cooked properly, and veggies must be fresh. Save that limp carrot in the veggie drawer for soup. And as for fish sauce, since it's a major component of the nuoc cham you'll be dressing this "salad" with, try to find a good brand; Golden Boy is my current favorite.
For starters, if your local Asian market has fresh rice noodles, you're miles ahead of the game. If not, soak the dried noodles in warm water to soften them, then cook them briefly in boiling water. (Soaking first keeps the outside from getting mushy by the time the inside is al dente.) After cooking, put the noodles in a bowl of ice water to stop cooking. I hold them in the cold water; it keeps them from sticking together.
For the meat, I like a marinade of minced lemongrass, minced garlic, fish sauce, soy sauce, sugar, lime juice, and oil. Eqaul parts of everything except the lemongrass and oil, use more (maybe 3x as much) of those. You can marinate chicken, pork, beef, or shrimp in this stuff before grilling. I love deep-fried shrimp paste cake on bun, but haven't had the nerve to look for a recipe yet, let alone try making it at home. If you do, please report.
For veggies, you definitely need carrots and cucumbers, and maybe some daikon and/or jicama. They're good just julienned or thinly sliced, but if you quick-pickle some or all of them in rice vinegar and sugar (I like to do the carrots and jicama), it gives them a little extra kick.
The nuoc cham that you pour over the salad is pretty straightforward. Buzz a couple of cloves of garlic, a seeded thai bird chile, a few tablespoons each of sugar and fish sauce, and some hot water in a food processor or a blender until there are no more recognizable chunks of garlic or chile. Squeeze in half a lime, being sure to get lots of pulp into the sauce. Taste and correct the flavors (you may want to add more lime, sugar, and/or water) and garnish with a tiny bit of finely grated carrot.
Assembly is straighforward. Put some shredded lettuce (butter lettuce is my favorite) in a bowl and top with noodles. Arrange bean sprouts, veggies, basil, and cilantro around the edges. Top with grilled meat. Garnish with finely chopped fresh-roasted peanuts. Serve nuoc cham on the side.
For an interesting twist, serve the constituent ingredients separately with rounds of rice paper (banh trang) and a bowl of hot water for softening the papers. Each diner dips a rice paper round in the water, then fills it with the desired ingredients before rolling it up like a burrito. Voila, do-it-yourself goi cuon!