Bok Choy Potato Gratin
8" cast iron skillet
chef's knife or cleaver
6-8 large red skinned or other waxy potatoes
1 head of bok choy (about 1 pound), diced
1 sweet white onion, diced
3 T unsalted butter (1 T for cooking the bok choy and 2 T for a béchamel)
2 T unbleached all purpose wheat flour
2 oz. each of 3 types of cheese (I used Havarti, chèvre, and Parmesan)
whole milk (enough to fill the space remaining in the skillet, about 1.5 cups)
Par cook the potatoes by boiling them whole in a Dutch oven with enough water to cover. Remove the potatoes to cool. Slice into 1/8" slices and set aside.
In the cast iron skillet, sauté the bok choy and onion in 1 T butter until onion is transparent. Turn down to medium and cook until caramelized. Remove and set aside.
Use <1 tsp of water to deglaze the skillet and turn back up to high. Melt 2 T of butter and add the flour. Once the flour is browned, add water and/or milk as desired to make a roux. Set aside (I usually just pour it into a teacup or measuring cup).
Preheat an oven to 400F. In the cast iron skillet, layer potatoes, bok choy mixture, cubed cheese, and béchamel until all ingredients have been used. Fill the skillet up to within 1/4" of the rim with whole milk and place in the oven. Cook until heated through and browned on top, about 40 minutes.