Easy Shrimp Corn Chowder

I made this at the cabin and it was well liked... so I decided to make it again tonight, but realized I had forgotten the potatoes and had to improvise. I think I like this version even better and it was way easier!

1 lb peeled de-veined shrimp
1 small onion
1 bag of frozen corn
1 bag of instant mashed potatoes (any flavor you want)
2T butter
2% Milk (maybe 6 cups?)
Cajun Seasoning (optional)

Chop onion.
Heat a large sauce pan and melt butter.
Add onion and sauté until softened and caramelized a bit.
Add about 6 cups of milk, the corn, and instant potatoes.
Bring to a boil. Let simmer for about 7 minutes.
Pull tails off of shrimp and cut into bite size pieces.
Add shrimp to pot and simmer for about 5 minutes, until shrimp are firm and opaque.
Season to taste - I added some white pepper, cajun seasoning, and salt.
**I added more milk as needed to keep the consistency I wanted. I used garlic flavored mashed potatoes. I think various flavors would be good. **