Light your charcoal in the KUDU and let them burn to embers with a layer of white ash.
While the charcoal is prepping rinse your sweet potatoes and kale.
Cut up your sweet potatoes into 1-2 inch squares, placing them into the cast iron skillet.
Tear the leaves of the kale off the stem, the bigger the pieces the better. Add to cast iron with the sweet potatoes.
Chop the garlic and spread over the vegetables.
Drizzle a little olive oil and salt & pepper over the vegetables.
Adjust your grill height over the embers to medium heat. To locate medium heat, place your hand over the embers and find that height you can count to 5 seconds before having to remove your hand from the flame (approx. 400 degrees).
Move your KUDU cast iron to this height.
Add a spoonful of duck fat and spread throughout vegetables.
Make sure all the sweet potatoes and kale spend some time cooking on the bottom of the skillet and turn them ever so often to cook thoroughly.
You want to remove the cast iron when the sweet potatoes are still al dente and the kale is wilted.
Remove and serve.