Heat a large pan with 2 tablespoons of oil over medium high heat. Add the onion, garlic, ginger, half of the chopped scallions, and Gochugaru. Saute until softened, about 2-3 minutes.
Add the ground pork, and sprinkle lightly with salt and pepper. Break it up with a wooden spoon and cook until the meat is no longer pink, about 3 minutes.
In a small bowl, stir together the soy sauce, sugar, Doenjang, and Gochujang. Add to the meat and stir to coat, about 1 minute. Add both of the peppers and cook briefly until slightly softened, about 1 minute.
Add 1 ½ cups of water to the pan, and bring it to a boil. Add the tofu to the pan, and spread into a single layer. Cook for 4-5 minutes, stirring once in awhile, to make sure the tofu doesn’t stick to the pan.
Stir in the cornstarch slurry mixture to thicken the sauce, and then the sesame oil. Cook for another minute, or until slightly thickened. Season with salt and pepper or more soy sauce to taste if needed. Garnish with the sesame seeds and remaining chopped scallions, and serve hot over rice.