1 lb. firm or extra firm tofu, drained and cubed
1/2 cup low sodium soy sauce or Bragg's All Purpose Liquid Soy Seasoning
2 tsp. yellow mustard
1 clove garlic, minced
1/3 cup oil
2 Tbsp. peanut butter
2 Tbsp. ketchup
Remove the tofu from the package and drain excess water. You will have to press the tofu to remove the rest of the moisture from it, which will make room for the tofu to absorb the marinade. Do this by placing the brick of tofu in a strainer or on a flat plate, then place another plate on top of it and put a heavy object on top to weigh it down. This will squeeze all the extra water out. Allow the tofu to drain for 30-60 minutes. Be sure to drain the water as it collects on the plate. You can also cut the tofu into 3-4 slices, sandwich them between a clean tea towel and use your palms to firmly press down on the tofu to squeeze out the moisture.
Once the tofu has been thoroughly drained, slice the brick into small cubes. In a medium size bowl or dish, combine the marinade ingredients. Add in the tofu cubes, cover, and refrigerate overnight. This will allow the tofu to soak up all of the flavours of the marinade. If you can't refrigerate it overnight then let the tofu marinate for at least 3-5 hours before cooking for best results.
After the tofu has marinated, heat a large skillet over medium-high heat. Remove the tofu cubes from the marinade and place in the skillet, cooking until just browned. Add in the reserved marinade sauce, and cook for 10-15 minutes, stirring frequently. The tofu is done when it is golden and crispy on the outside but still spongy on the inside.