Preheat the oven to 450 degrees. Place a 10-inch cast-iron skillet in the oven to heat.
For the scallion-pimento cheese: Stir together the cheese, pimentos, mayonnaise and scallions in a large bowl. Set aside, or if making ahead, place in the fridge until ready to use.
For the country ham biscuits: Mix the flour, baking powder and salt in a bowl. Using a pastry blender or 2 table knives, cut the cold butter cubes into the flour until it resembles coarse meal. Use a fork to stir in the buttermilk to make a soft dough that comes together and leaves the sides of the bowl (make sure all the flour is worked in). Stir in the ham. Turn the dough out onto a lightly floured board and knead 3 or 4 times until smooth and manageable.
With your hands or a floured rolling pin, flatten the dough to a thickness of 1/2 inch. Cut the dough out with a 2-inch floured biscuit cutter.
Remove the skillet from the oven and melt the remaining 1 tablespoon butter in it. Place the biscuits in the skillet. Bake until lightly browned, 10 to 12 minutes.
To serve: Split the biscuits and serve with a generous spread of pimento cheese.