Make the filling: Reduce heat to medium and transfer in the a pan the olive oil, the onion, the corn, the peppers. Cook until the onion is soft and then add the minced beef, the beans, the parsley, the green onions, and the tomato. Cook for 2 more minutes and turn off the heat. Add half of the grated cheese, the yogurt and the avocado and mix.
PRO TIP: Don't be afraid to brown (caramelize) the meat very well. The dark color means great flavor! Remember that the caramelization will start when all the juices of the meat have evaporated.