Preheat oven to 325 degrees.
Peel the sweet potato and cut it into 2 inch x 1/2 inch x 1/2 inch sticks. Toss the sticks with olive oil and garlic salt to coat.
Arrange the fries in a single layer on a cookie sheet and bake for 15 minutes. Flip all fries and bake for another 10 minutes, until all fries are golden.
While the fries are baking, make the chipotle mayo sauce by combining the mayonnaise, chilies, and adobo sauce in the bowl of a food processor. Pulse until smooth. Mix with the ketchup if desired.
When the fries are done, let cool for a few minutes. Pat any excess oil off with a paper towel and sprinkle with salt.