Light your charcoal in the KUDU and let them burn to embers with a layer of white ash.
While the charcoal is prepping prepare your cauliflower and broccoli.
Cut up your cauliflower and broccoli placing the florets into the cast iron skillet.
Drizzle a little olive oil and salt & pepper over the cauliflower and broccoli.
Adjust your grill height over the embers at medium heat. To locate medium heat, place your hand over the embers and find the height you can count to 5 before having to remove your hand (approx. 400 degrees).
Move your KUDU cast iron to that height.
Add a spoonful of duck fat.
Make sure all the cauliflower and broccoli spend some time cooking on the bottom of the skillet and turn them ever so often to cook thoroughly.
You want to remove the cauliflower and broccoli when they are al dente.
Remove and serve.