Fry the bacon in a 10-inch skillet until crisp, about 8 minutes. Remove the bacon and drain on paper towels. Combine the onion, chicken broth, au gratin potato mix (both the potatoes and sauce mix), water, undrained corn, and pepper with the bacon in a 3 1/2-quart slow cooker. Cover and cook, on the low setting, 6 hours.
Add the salmon, milk and evaporated milk. Cover and cook, on the high setting, 15 minutes or until thoroughly heated.