Dice the tofu and cut the onion, green onion, zucchini, and mushrooms into bite-sized pieces.
Heat cooking oil in a pan and brown the tofu on all sides.
Remove the tofu, then sauté the onion, green onion, zucchini, and mushrooms in the same pan.
When the vegetables are partially cooked, add doenjang (soybean paste), gochujang (Korean chili paste), minced garlic, and water, then bring to a boil.
Return the tofu to the pan and simmer together.
Spoon the finished tofu soybean paste sauce over rice and garnish with chopped scallions and sesame seeds.