Heat the olive oil in a Dutch oven over medium heat. Add the onion and cook until tender and translucent, 5 to 6 minutes. Add the chicken and cook, using a wooden spoon to break it up as it browns, about 5 minutes. Mix in the taco seasoning and 1/4 cup water. Cook for 3 minutes. Add the tomatoes, salsa, beans, corn, salt and pepper. Bring to a simmer, reduce the heat to low, cover and cook until reduced slightly and heated through, about 20 minutes. Serve with sour cream, cheese, scallions and jalapenos.