Beat egg until lightly foamy.
Add lupin flour and whisk until smooth.
Add milk and whisk again, making sure there are no lumps.
Rest the batter while you heat a small (20cm/8") frying pan (U.S. option HERE) smeared with a tiny bit of coconut oil (medium-low heat/induction 7).
Whisk and pour 55g of batter (about ½ of the recipe unless you've changed servings) into the pan; tilt it so it spreads evenly all over the bottom.
Cook for a few minutes until opaque on top, raise the heat, then check by lifting the edge with a flexible spatula - if it's dry and lifts up easily, flip it over and cook the other side (it helps to slide a spatula underneath in case it's stuck in places); if not, leave it to cook for longer or it will brake when lifted.
Flip again a couple of times - both sides should be dry, with brown speckles, otherwise you'll end up with crêpes, rather than 'tortillas'.
Give the remaining batter a quick whisk and make the second 'tortilla' in exactly the same way as the first one.
Serve with anything you can think of.
