In a small bowl, whisk together all of the ingredients for the marinade.
Cut the tofu into 1 inch cubes, or in small triangles. For triangles, cut the block of tofu in half down the long part of the block so you have 2 blocks the same size as the original, but half the thickness. Keeping the 2 pieces stacked, cut them in half from top to bottom (along the long side). Then start cutting width wise - i.e. cut the stack in 2. Cut each of those halves in 2. You will now have 16 flat squares. Cut these in half on the diagonal so each square now becomes 2 triangles.
Pour the marinade into a baking baking tray (I used 7x11). Place all of the tofu onto a single layer in the marinade. Let sit for at least 30 minutes, flipping the tofu once. If you're doing this several hours or the day before, keep refrigerated.
Heat a stove top grill pan or a skillet over medium heat. Brush the grills with sesame oil, or if using a skillet, add about a tbsp sesame oil. Once hot, add the tofu pieces in a single layer (keep the marinade.) Cook for about 4-5 minutes per side, until heated through and some nice sear lines appear (if using the grill). When the tofu is done, place it on a plate under some foil to keep warm.
Grease the pan with sesame oil, and cook the shiitake mushrooms in a single layer. Cook for for 2-3 minutes, flip them, and cook for another 2-3 minutes. Remove pan from heat.
Pour the remaining marinade, half over the tofu and half over the shiitake mushrooms. Toss to coat.
Prepare the noodles according to package directions in a pot that is big enough to also hold the bok choy. Two minutes before the noodles are ready, place the baby bok choy on top of the noodles to briefly cook. Do not stir so they don't become tangled up in the noodles. Drain when the cooking time for the noodles is up.
To serve, ladle some broth into bowls, add noodles and then top with the tofu, shiitakes, baby bok choy, green onions and sesame seeds. Enjoy with hot sauce of choice or chili flakes, if desired.