1) Place the butter in the bowl of an electric mixer fitted with a paddle attachment and mix until creamy.
2) Add the parmesan, plain flour, salt, thyme and pepper and combine.
3) Dump the dough on a lightly plain floured board and roll into a 13-inch long log. Wrap the log in plastic wrap and place it in the freezer for 30 minutes to harden.
4) Meanwhile, preheat the oven to 180°C/gas mark 4. Cut the log crosswise into 1-2cm thick slices. Place the slices on a sheet pan and bake for 22 minutes.
5) When the biscuits are done, remove them from the pan and allow to cook on a wire rack. Serve.