01 -
Set your oven to heat up to 375°F (190°C).
02 -
Coat the inside of a big ceramic baking dish (around 10 × 14 inches) well with some cooking spray.
03 -
In a big bowl, combine sliced rosemary, shredded asiago, shredded smoked gouda, pepper, paprika, sage, garlic powder, and salt. Put aside once done.
04 -
Lay down one single layer of sweet potato slices in your prepared baking dish.
05 -
Spread a layer of onion slices on top of the potatoes.
06 -
Evenly scatter half of the cheese and spice blend over the onions.
07 -
Place another layer of sweet potato slices, add more onions, and finish with one more layer of potatoes on top.
08 -
In a large bowl, whisk together sour cream, milk, heavy cream, butter, and cornstarch until smooth with no lumps.
09 -
Carefully pour the creamy mixture all over the potato layers so it’s evenly distributed.
10 -
Sprinkle the other half of your cheese mixture over the top layer of potatoes.
11 -
Put on the middle rack and bake (uncovered) for anywhere between 1 hour and 15–30 minutes. It’s ready when the cheese is bubbly and golden, and the potatoes are tender.
12 -
Let it sit and cool for at least 15 minutes before cutting into it. This helps everything set up and cool to a good eating temperature.