Preheat oven to 450° F.
Heat a large oven-proof skillet to medium then add 6 TB butter. Once melted, add apples, brown sugar, cinnamon, nutmeg and salt. Stir to combine and cook for 5-10 minutes or until slightly soft. (If you like them softer, cook longer) Turn off heat and set aside.
In a medium-sized bowl, add flour, baking powder, sugar and salt. Stir to combine. Add melted butter and milk. Stir until just moistened.
Add cooked apples to biscuit batter and fold to combine. Do not scrape the cinnamon/butter mixture off the bottom of the skillet. Leave some for the biscuits to cook on top of.
Using a large scoop, drop about 1/3 cup size batter into skillet until all batter is used. The batter might spread some but that's ok. Place skillet in oven and bake biscuits for 10 minutes or until light golden brown.
While biscuits are baking, make the glaze by whisking together powdered sugar, vanilla, and milk. Add more powdered sugar if it's too thin or more milk if it's too thick. Needs to be a pourable but thick consistency.
When biscuits are done, remove from oven and drizzle glaze over the top. Serve immediately.