2 large organic sweet potatoes, washed and sliced 1/4 inch thick
3 lbs organic yellow fleshed potato, peeled and sliced 1/4 inch thick
1 tbsp organic rosemary, chopped
Preheat the oven to 350°F, and move a rack to the middle of the oven. Cut a piece of parchment paper to fit over a 10” cast iron pan.
In the cast iron pan, cook the onions and garlic with butter, salt, pepper and the thyme until soft and beginning to caramelize. Add the cream and milk. Bring to a simmer and allow to thicken slightly. Remove from the pan and set aside.
Lay potato slices around the pan overlapping and alternating then fill in the middle. Cover the layer with ⅓ of the cooked onion mix and a sprinkle of chopped rosemary. Repeat with 2 more layers. When the final layer is finished carefully pour on the remaining cooked onion mix.
To cook, cover with a piece of parchment paper and place on a baking sheet to catch liquid if it leaks over.
Bake 40 minutes, then begin checking for doneness by poking with a knife. The knife should pass through the layers easily. Continue to cook until most of the liquid is gone and a knife passes easily through the potatoes. Approximately another 30 minutes.