Blend the oats to a coarse flour in a food processor
Add the flour
Add the grated butter
Blitz until it resembles breadcrumbs
Add the sugar, salt and bicarbonate of soda
Add enough milk to bring the dry ingredients together
Continue blitzing to form a coherent dough
Spread clingfilm on your work surface, with enough left to wrap around the flattened dough.
Put your dough ball down on the cling film and press into a flat disc, you can use a rolling pin for this.
Wrap the extra cling film around the disc, and place flat in the fridge for 20–30 minutes. This will make the butter harden slightly, and the dough easier to work with.
Remove the dough disk from the fridge, place it on your work surface and start rolling – with the cling film!
You're aiming towards a 4–6mm thick sheet.
Use a 45–60mm cookie cutter and stamp out as many biscuits as you can from the sheet, lifting them with a spatula and placing them on a baking tray lined with parchment paper or reusable teflon baking sheets.
Once all the biscuits are removed, fold the dough over and repeat: roll, cut, lift. Until all the dough is used up.
Before baking, use a fork or similar implement to make some patterns on the raw biscuits.
Bake in the middle of your pre-heated convection oven at 170˚C for 12–14 minutes depending on how crunchy or soft you like them.