Preheat your oven to 425° WITH your cast iron pan inside.
Start by measuring your flour and placing it in your bowl. Put your bowl with the flour in the freezer.
While your flour bowl is in the freezer, remove your butter and buttermilk from the fridge and measure the correct amounts. Place the 1/2 C. butter on a separate plate and leave your 1 C. buttermilk in your measuring cup.
Remove your cold flour bowl and cut in your butter until you have a nice crumbly consistency.
Add buttermilk and mix it up good! I use a spatula. You can use a dough hook, a spoon, a fork...whatever suits your fancy, really!
Scoop your dough onto a clean, floured surface and knead it just long enough for it to hold a ball shape.
CAREFULLY take your cast iron pan out of the oven. It will be hotter than Florida summer asphalt, so again, be careful. I've burned my hands up one too many times to not say it twice!
Drop your 1 TBSP butter in your hot cast iron pan and pull apart even balls from your big dough ball, shape it, and plop it into your cast iron skillet. Listen to that sizzle!
Return your pan to the oven and bake until your biscuits are just lightly tanned on top.
Lather them up hot with some butter and jam and enjoy! This is optional...I'll try not to judge you if you decide to skip this step. (just kidding, this is a #judgment-free zone!)