At least 1 hour before (overnight is better), marinate the beef: crush 1 tablespoon of sugar, half the ginger, 2 cloves of garlic, half the lemongrass, and 1 Thai chili in a mortar and pestle. Combine with the thinly sliced beef, along with 1 tablespoon each of fish sauce, oyster sauce, and oil. Mix well, then cover and store in the fridge.
At the same time, make your fish sauce: combine the remaining 2 tablespoons of sugar, 1 tablespoon of ginger, 4 cloves of garlic, and 2-4 Thai chilies (as comfortable) in a mortar and pestle. Crush into a fine paste, then transfer to a jar along with 2 tablespoons of fish sauce and 1 cup of water. Store in the fridge.
When you are ready to eat, cook your vermicelli to the time indicated on the package (usually 3 minutes), then drain and rinse well with cold water. Set aside. Prepare your vegetables. In the photo, I used quick pickled cucumbers, purple cabbage, lettuce, cilantro, lime, and fried onions.
To make quick pickled cucumbers, thinly slice 1/4 of an English cucumber, then toss with 1 teaspoon salt and 1 tablespoon sugar. Let sit for 15 minutes, then rinse in cold water.
Heat a large nonstick skillet with 1 tablespoon of oil over medium heat. Fry your remaining 1 tablespoon of minced lemongrass until crispy and golden brown, then drain and set aside, reserving the oil.
Add the marinated meat to the skillet and fry until well charred on both sides. You may need to do this in batches depending on the size of your nonstick skillet.
Arrange vermicelli, vegetables, and beef in a bowl. Toss with 1/4 cup of the fish sauce, then top with fried lemongrass, fried shallots, a squeeze of lime, and sliced chilies, as desired.