Preheat oven to 375 degrees F. Spray an 8x8 inch pan with nonstick cooking spray or grease with butter or oil.
Arrange sweet potatoes: Place sliced sweet potatoes in three tight slanted rows as indicated in the photos. You don’t want them to be overly tight, make sure you leave enough space so the sweet potato slices are slightly slanted.
Make the sauce: add in 3 tablespoons of butter and place over medium heat. Once butter melts, whisk in the flour and cook for 10-20 seconds until a paste forms, then very slowly add 2 cups of the milk, while you continue to whisk away any lumps. You’ll need to whisk pretty vigorously but it should smooth out easily.
Once smooth, bring mixture to a simmer for a few minutes, stirring every so often until sauce thickens up a bit, similar to a gravy. If it gets too thick, add in a few tablespoons more milk. Taste sauce and add more salt as needed.
Once thick, turn off the heat and stir in 2 cups shredded gouda cheese (reserving 1/2 cup for later), garlic powder and 3 tablespoons of the sauce from the can of chipotle chiles. Season with freshly ground salt and pepper, to taste. After tasting the sauce, you can decide if you want to kick it up a notch and add in 1 more tablespoon of the chipotle sauce. I definitely recommend it!
Pour the sauce evenly over the sweet potatoes to cover them. Don’t worry, the sauce will get nice and creamy while baking.
Cover the pan with foil, then bake for 45 minutes-1 hour. The sweet potatoes are done when the middle sweet potatoes can be easily pierced with a fork.
Once they are done baking, remove the foil, sprinkle ½ cup remaining gouda cheese and 1/4 cup parmesan cheese on top, then turn on the broiler in your oven and broil on high for 1-2 minutes (watching carefully so they don't burn!) or until cheese is nice and melted and slightly golden brown. Remove from oven and garnish with fresh chopped parsley. Enjoy!