Heat 2 tablespoons of olive oil in a large skillet over medium-high heat until hot, add the eggplant cubes and cook them, covered, occasionally stirring, for about 3-5 minutes, until they begin to soften and get brown around the edges. NOTE: Mid-way through the cooking (after about 2 minutes), add a touch of salt over the eggplant, stir, and continue cooking for about 2 more minutes. Remove the eggplant to a plate and set aside. It should be browned and just a little bit soft (you will cook it more thoroughly later).
Add another tablespoon of olive oil to the same skillet, add chopped onion and diced garlic and cook, stirring, for 1 minute over medium-high heat. The finely chopped onions should get very soft and even brown a bit.
Add chopped red bell pepper, stir with onions and garlic and cook for about another minute over medium-high heat, regularly stirring, covered.
Add soy sauce, fish sauce, red curry paste, and water to the skillet and stir quickly on medium-high heat until smooth. Immediately reduce heat to low. Return the eggplant to the skillet, along with 2 cups of cooked quinoa (the quinoa should already be cooked!)
Stir all ingredients well. Add another ½ cup water to the skillet. Continue cooking (simmering) on very low heat for about 5-10 minutes (or longer), until almost all liquid is absorbed and the eggplant is soft. In other words, cook long enough so that eggplant acquires the right texture (soft but not mushy - so, keep watching cooking time), and keep adding water if the sauce gets absorbed too fast and if vegetables and quinoa start sticking to the pan. That way you get soft eggplant and flavorful quinoa.
Before serving, add sesame oil, half of chopped green onions, stir everything well. Serve topped with the remaining half of chopped green onions.