In a mixing bowl, combine soy sauce, dark soy sauce (if using), corn starch, sugar or liquid sweetener, rice vinegar or lemon juice, ground pepper, and chili garlic sauce (optional). Whisk until smooth and well incorporated, ensuring no lumps remain. Set the sauce aside while you move on to the next steps.

Bring a medium pot of water to a rolling boil over high heat. Once boiling, add the instant ramen noodles and cook for about 3 minutes, which is 2-3 minutes less than the package instructions for al dente. Drain the noodles and rinse them briefly under cold water to stop the cooking process, then set aside.

In a large pan or skillet, heat a tablespoon of oil over medium-high heat. Add your choice of vegetables and the extra firm tofu, diced into cubes. Sauté for 5-7 minutes, stirring frequently, until the vegetables are tender and the tofu is golden brown.

Pour the prepared sauce into the pan with the sautéed vegetables and tofu. Reduce the heat to medium and let it simmer for 2-3 minutes until the sauce thickens and becomes glossy.

Add the drained ramen noodles to the pan, tossing them in the thick sauce gently. Cook for an additional 3 minutes, stirring continuously, until the noodles are heated through and nicely coated in the sauce.

Taste your saucy ramen noodles and adjust the seasoning if necessary. Serve hot, garnished with chopped scallions and a sprinkle of sesame seeds.