Dissolve the cornstarch in 1 cup of the milk and set aside. Heat the butter in a large saucepan or soup pot and sauté the onion and garlic until soft and translucent—about 8 to 10 minutes. Add the spices and stir to blend.

Cut the corn off the cobs, then run the back of a knife down the cobs to extract the milk. Add the corn and corn milk to the pot to warm, then carefully transfer the mix to a blender or food processor. While the machine is running, add the reserved cup of dissolved cornstarch and milk. Return the mixture to the pot over medium heat.

Stir in the masa harina and cook until thickened.

Add the chopped green chiles and simmer for 5 minutes.

Serve hot, garnished with fresh cilantro, grated cheddar cheese, and tortilla chips.