Special equipment: a small jar or container with a lid; a bamboo steamer
Preheat the oven to 400 degrees F.
In a large bowl combine the carrots, onions and daikon radish. In a small jar or container with a lid, combine the vinegar, fish sauce, 2 teaspoons of the sambal, the sugar, ginger and half of the garlic. Shake well and rest until the sugar dissolves and the flavors marry, at least 15 minutes. Add the vegetable mixture to the pickling liquid and shake. Marinate at room temperature for 1 hour.
In a small bowl, combine the hoisin, maple syrup and the remaining 2 tablespoons sambal. Brush the hoisin mixture on both sides of the bacon, then place on a baking rack set in a baking sheet. Bake the bacon for 5 minutes, then brush with the hoisin mixture on both sides. Cook until bacon is sticky and crackly, about 25 minutes.
Meanwhile, coat a saute pan with some oil. Add the remaining garlic and cook until aromatic. Add the mushrooms and cook until wilted. Then add the soy sauce, toss to coat and remove from the heat.
Line a bamboo steamer with the cabbage leaves, then add the bao buns and steam until soft and warm, 6 minutes.
Place a slice of cucumber in each bun. Top each with a slice of bacon, some mushrooms, pickled vegetables, sprouts, peanuts and cilantro to serve.