Begin by thinly slicing the carrot and cucumber. If desired, lightly salt them and set aside to drain any excess moisture. In a bowl, mix rice vinegar, sugar, and a pinch of salt until dissolved; stir in the sliced vegetables. Let them marinate for about 10-15 minutes.

While the veggies are pickling, heat a tablespoon of neutral oil in a skillet over medium heat. Sauté minced garlic for about 30 seconds, then add sliced mushrooms. Stir in hoisin sauce and maple syrup; cook for 5-7 minutes until mushrooms are tender.

In a mixing bowl, combine all-purpose flour, corn starch, and salt. In a separate small bowl, whisk warm soy milk with sugar and instant dry yeast until foamy, about 5 minutes. Pour this yeast mixture and a tablespoon of oil into the flour mixture. Mix until a dough forms and knead for about 8-10 minutes until smooth. Let it rise in a warm spot for approximately 1 hour.

Once the dough has risen, gently punch it down to remove air. Divide into 12 pieces, shaping each into a smooth oval bun. Brush the tops with oil, place on parchment paper, and let proof for another 15-20 minutes.

Set up your steamer over simmering water. Place buns in the steamer basket, cover and steam on medium heat for 8-10 minutes, or until fluffy. Allow to rest a few minutes before removing.

To assemble, split open each bun and fill with hoisin mushrooms and pickled vegetables. Optionally include vegan kimchi, and top with peanuts and spring onions.