Preheat oven to 450°F (230°C).
Place 1 tablespoon of butter into a cast iron skillet and place the skillet in the oven to heat up and melt the butter. Watch closely so it does not burn.
In a large bowl, mix together the baking mix, shredded cheddar cheese, diced ham, and green onions.
Pour in the milk and mix well until just combined. The mixture will be quite wet and sticky. Do not overmix.
Carefully remove the hot skillet from the oven. Using two spoons, drop mounds of the sticky dough into the hot, buttered skillet. (Alternatively, pour the entire mixture in and spread gently to cut into wedges later).
Bake for about 20 minutes, or until the biscuits are a deep golden brown and cooked through in the center.
Melt the remaining 1 tablespoon of butter. Remove the skillet from the oven and immediately brush the hot biscuits with the melted butter. Serve warm!