In a large saucepan add the shredded chicken and green chile sauce. Simmer uncovered, 10 minutes. Stir to mix and heat evenly.
Place 6 tostada shells on lined baking sheet. Divide half the green chile chicken over the first layer of shells. Top each with a third cup of cheese and repeat with another layer of tostada shells, both green chile chicken and cheese.
Place baking sheet under the broiler to melt cheese. Top with any remaining green chile sauce in pan, jalapeño slice or chopped cilantro and serve hot.