First, add just enough mushroom broth to the stewpot to loosen the browned onions from the bottom of the pan. Continue cooking and browning, adding small splashes of broth as needed, until the onions are very dark brown.
At the same time, in a large skillet, pour in 1/4 cup mushroom broth and add the cubed tofu. Brown the tofu on all sides over medium-high heat, adding more broth when it starts to stick, loosening the cubes and cooking until they start to stick again. Once the tofu cubes are well browned, add them to the stewpot with the onions, along with the rest of the mushroom broth. If more liquid is needed, add water to just cover the stew ingredients.
In the same skillet, use water to brown the carrots and mushrooms following the same process: sear, loosen with water when they stick, and continue browning. Add them to the stew mixture once done. Finally, stir in the crushed garlic, cover the pot, and let the stew simmer until the flavors have fully developed and everything is tender.