Savoury oatmeal biscuits

SOURCE This recipe is adapted from Marietjie and Jaco Swart's Rainbow Cooking website.
The original recipe called for 2 tablespoons of sugar; we were trying to approximate the taste of savoury Scottish oatcakes, so left it out. We also added the ground black pepper.
This recipe can be 'veganised' by substituting aqua faba for the egg and using coconut oil rather than butter: 3 tablespoons of aqua faba = 1 egg. (Aqua faba is the cooking liquid of chickpeas or other legumes and is used as an egg-white substitute: the simplest way to get it is to drain a can of chickpeas (with no added salt or sugar). You can add the chickpeas themselves to a salad or use them to make hummus.)
Makes c.80 biscuits, using a 5cm round biscuit cutter
Time (approx): preparation 20m cooking 15–20m (per batch: you'd need a very large baking tray to get it all done in one go)

360g porridge oats
100g flour
1 tsp baking powder
1 tsp salt
1 tsp ground black pepper (optional)
130g coconut oil or chilled butter*
1 egg (or 3 tbsp aqua faba)
c.250–260ml milk**
* Use odourless coconut oil refined for cooking use; ordinary coconut oil works perfectly well but imparts a definite coconut flavour which is not at all unpleasant but detracts from the 'Scottish oatcake' effect.
** The original recipe specifies "enough milk to fill a 3/4 cup after the egg has been cracked". We tried cracking an egg into a standard 250ml cup and then filling with milk, but the resulting mixture was very dry and crumbly, especially when using coconut oil.
Weighing scales
Measuring spoons
Food processor
Rolling pin (or clean large glass bottle with all labels etc removed)
Biscuit cutter (or you could use the rim of a small cup)
Baking tray
Baking parchment (unless baking tray is genuinely non-stick)
An oven for cooking; Space to roll out the dough.
Advance preparation
None required, apart from pre-heating the oven to 200°C / 390°F / Gas Mark 6.
Preparation and cooking
Add the porridge oats to the food processor and process for a short while until they are ground to a rough powder.
Add the flour, baking powder, salt, and pepper (if using); give a short pulse with the processor to mix.
Add the coconut oil or butter in small chunks; process until the bits of oil/butter are no bigger than lentils.
Add the egg (or aqua faba) and milk; process until the dough is well mixed and holds together. It should be a bit damp but not 'slimy'; sometimes, it is not possible to be sure that it is wet enough until you start rolling it out.
Remove the dough from the food processor and make three roughly equal-sized balls out of it: it is easier to roll out if there is not too much at a time. On a well-floured surface, roll out one of the balls with the (floured) rolling pin or bottle until the dough is 2–3mm thick. (If the dough crumbles on rolling, no problem: just break up the dough a bit, return to the food processor, add a little more milk and process it again.)
Cut out the biscuits using the cutter, then repeat for this and the remaining balls until all the dough is used. Line the baking tray(s) with parchment and place the cut-out biscuits on the parchment.
Bake for 15m on the centre shelf of the oven; when done, the biscuits should be just turning light brown at the edges. If they are not done, leave them in for a little longer, checking at two-minute intervals: they can flip very quickly from being not-quite-done to being overdone.
Put the biscuits on a wire rack to cool; if cooking in batches, put the next batch on the tray and bake as above. Store in an airtight container.
Suggested accompaniments
These biscuits pair very well with cheese or dips such as hummus. They are also great on their own: ideal as 'good carb' snacks at work or out and about.