Seed and dice 2 of the jalapenos. Slice the remaining one jalapeno into thin rounds.
In a bowl, beat cream cheese, mayonnaise and garlic powder with a hand mixer on LOW speed until smooth and fluffy.
Add 2 cups of the shredded cheese, green chilies and diced jalapenos.
Transfer cream cheese mixture into a cast iron skillet or baking dish and spread evenly with a spatula.
Top with remaining ½ C cheese and the sliced jalapenos.
Bake in a 375°F oven for about 15 to 20 minutes or until hot and bubbly and top is lightly browned. Serve immediately.