Soak rice and prepare batter: If using rice flour, mix 2 cups rice flour with 3 cups water and 1/2 tsp salt. Whisk until smooth and let rest 30 minutes. If making from scratch, soak 2 cups rice overnight, drain, blend with water until smooth, and strain.

Prepare filling: Heat 1 tbsp vegetable oil in a skillet over medium-high heat. Sauté minced garlic and diced onions until fragrant, about 2 minutes. Add ground pork, breaking it up with a wooden spoon. Season with 1 tsp fish sauce, 1/2 tsp black pepper, and cook until fully cooked, about 8 minutes. Stir in chopped mushrooms and cook 3 more minutes. Set aside to cool.

Make nuoc cham sauce: In a bowl, combine 3 tbsp fish sauce, 3 tbsp lime juice, 2 tbsp honey, 1/4 cup water, 1 minced garlic clove, and sliced red chili. Stir well and set aside.

Prepare steaming setup: Stretch a thin cotton cloth tightly over a large pot of boiling water, securing with string or the pot lid edges. Oil the cloth lightly with vegetable oil.

Steam rice sheets: Ladle a thin layer of batter onto the oiled cloth, spreading quickly in circular motion. Cover and steam for 1-2 minutes until sheet is translucent and cooked through. Use a spatula to carefully lift edges.

Fill and roll: While sheet is still on cloth, place 2 tbsp of pork-mushroom filling in center. Using the spatula, fold the sheet over filling and roll into a cylinder. Transfer to serving plate.

Repeat process: Re-oil cloth between each sheet. Continue until all batter and filling are used.

Prepare toppings: Fry thinly sliced shallots in oil until golden and crispy. Drain on paper towels. Arrange fresh cilantro, mint, and lettuce on serving plate.

Serve immediately: Arrange rolls on plates, drizzle with crispy shallot oil, sprinkle with fried shallots, and serve with fresh herbs and nuoc cham dipping sauce.