For the pickles:
Julienne a few carrots and half of a daikon radish and combine with 1/4 cup sugar and 1 tbsp salt. Put everything in a jar along with 1 cup water and 1/2 cup rice wine vinegar, and store it in the fridge overnight.
For the bao:
In a saucepan, warm 1/2 cup plant (or dairy) milk and 1/3 cup water to about 110°F. Combine it with 1 tbsp active dry yeast, 2 tbsp sugar, and 2 tbsp vegetable oil in a small bowl. Leave it for 10 minutes or until the mixture gets nice and foamy.
In a large bowl, stir together 2 1/2 cups all-purpose flour, another 2 tbsp sugar, 1/2 tsp baking powder and 1/4 tsp salt. Add the yeast mix to the dry ingredients and combine. Use a stand mixer on medium or knead by hand until the dough is soft and elastic but not sticky (8 minutes by hand, half that if using a mixer). Form the dough into a tight ball, place it back in the mixing bowl and let it rise, covered, for about 2 hours or until the dough has tripled in size.
Turn dough out onto a counter and roll it about 1/3" thick. Cut 3 1/2" circles using a cookie cutter or drinking glass. Recombine any dough scraps and roll out to get a few more circles.
Brush each dough circle with a bit of oil, fold into a half circle, and gently flatten one more time with a rolling pin. Place the folded buns onto a steamer basket lined with parchment. Cover and let rest for another 30 minutes.
Bring water to a boil in a pan large enough to hold your steamer (not so deep that it reaches the buns). Place the steamer basket into the pan and cover, keeping the water at a simmer. Steam for 10–14 minutes, moving the lid slightly ajar for the last 2 minutes.
For the BBQ pulled mushrooms:
Preheat oven to 400°F. Trim any tough stems of 4–8 oz of oyster mushrooms (1 or 2 clusters), and tear into strips. Heat 3 tbsp vegetable oil in a pan on medium-high heat. Add mushrooms and sauté 7–10 minutes, stirring occasionally, until mushrooms are browned. Season with a bit of salt, pepper, and garlic powder.
While the mushrooms are sautéing, make the sauce. Combine 1 tsp fresh grated ginger, 1–2 sliced scallions, 1/2 cup ketchup, 2 tbsp rice vinegar, 1/4 tsp garlic powder, 1 tsp sesame oil, and 1 tbsp each hoisin sauce, vegetable oil, sriracha, soy sauce, and honey.
Pour the sauce over the sautéd mushrooms and transfer to a rimmed baking sheet or casserole dish (or keep it right in the pan if it's oven-safe). Bake for 20 minutes.
For the sriracha mayo:
Add 1–2 tbsp sriracha to 1/4 cup vegan mayo.
Assemble! Fill the bao with the saucy mushrooms, pickled veggies, and a dollop of sriracha mayo. Garnish with scallions, sesame seeds and cilantro.