Make pickled carrots. In a glass jar with a lid, add the rice vinegar, water, and granulated sugar. Shake until the sugar has dissolved, then add in shredded carrots. Push the carrots down to submerge them in the liquid (a muddler works great for this), put the lid back on, and store in the fridge until ready to assemble your sandwich. Preheat oven. Preheat oven to 400ºF/200ºC and line a rimmed baking sheet with parchment paper.
Make marinade. In a small bowl whisk together hoisin sauce, honey, ketchup, reduced sodium soy sauce or tamari, toasted sesame oil, Chinese five spice, and minced garlic until smooth.
Prep tofu. Remove the block of tofu from the package and pat dry using paper towels or a clean towel. Use a sharp knife to cut the block into thin ¼ inch slabs then place each piece directly on the prepared baking sheet in a single layer with a little space in between each one.
Brush and bake. Generously brush the sauce on the top and sides of the tofu (you’ll have sauce leftover to brush the other side once cooked). Bake for 18 minutes, carefully flip the tofu slices, brush with the remaining sauce and bake for another 10 minutes or until the edges start to brown slightly.
Assemble. Slather mayo or kimchi mayo on each side of the toasted bread then layer a few pieces of tofu, top with cucumber and jalapeño if using, followed by pickled carrots and fresh herbs. Slice in half and enjoy!