Preheat the oven to 425°F.
Prep Tofu: Transfer the tofu cubes to a reusable container or Ziploc freezer bag and add 1 tablespoon cornstarch. Seal the container and toss the tofu inside until it is evenly coated with the cornstarch.
Tofu: Transfer the tofu to a large non-stick baking sheet and place in a single layer.
Broccoli: In a medium bowl, mix the broccoli florets with the oil, and salt and rub the florets until evenly coated. Transfer the broccoli to the baking sheet with the tofu and place in a single layer.
Bake for 10 minutes before flipping over the florets and tofu so they cook evenly. Bake for about 10 minutes more, or until the tofu is crispy and the broccoli is slightly charred. (Optional: change the oven setting to broil and cook for about 2 minutes more, or until the tofu is extra crispy and the florets are charred.)
Prepare & Cook Sauce: While the tofu and broccoli are baking, prepare the sauce. In a medium bowl, mix the tamari, rice vinegar, maple syrup, mirin, garlic, and ginger. Heat the sauce in a large skillet over medium-high heat. Once it starts to bubble, reduce the heat to low and continue to cook until it starts to caramelize. Add water as needed to taste.
Optional: For a thicker sauce, in a small bowl, mix 2 teaspoons cornstarch with 1 tablespoon plus 1 teaspoon water until it dissolves fully. Add the cornstarch slurry to the heated sauce and stir until the sauce thickens.
Combine: Transfer the tofu and broccoli to the skillet with the sauce and mix to combine. Serve immediately with a grain of your choice.