Melt 3 tbsp butter in a skillet. Over medium heat, sauté the chopped onion and minced garlic for about 5 minutes.
To the skillet, add shredded chicken, corn, diced green chilies, cilantro, cumin, chili powder, salt, and pepper. Mix to combine.
Add 1 1/2 cup shredded Monterey Jack and mix once more.
In a sauce pan, melt 3 tbsp butter and thoroughly mix in 3 tbsp flour. Stir for about 1 minute over medium heat. Then quickly stir in 1 grated garlic clove.
Slowly pour in the chicken stock as you stir it into the butter and flour mixture. Then bring it to a simmer for 4-5 minutes or until it begins to thicken slightly.
Add the sour cream to the sauce and continue to stir until the sour cream is well incorporated.
Then stir in the salt and black pepper.
Spread a thin layer of the white sauce onto the bottom of a 9 x 13 inch baking dish.
Pour 3/4 cup of the sauce into the chicken filling mixture. Mix well.
Scoop about 1/4 cup of the chicken filling into each flour tortilla. Roll them up and place them tightly next to eat other into the baking dish.
Pour the remaining white sauce over the rolled up enchiladas, and top with the remaining 1/2 cup Monterey Jack cheese.
Cover with foil and bake at 370 degrees Fahrenheit on the middle rack for 40-45 minutes or until bubbly. Then remove the foil and bake until the top is golden brown.