Preheat oven to 425°F (218 °C) and have a shelf set about ¾ way up with an old baking tray on it. The tray must be preheated with the oven.

In a medium bowl, add the all purpose flour, chickpea flour, baking powder, and salt, and whisk them together. As I mention in my post, I highly recommend weighing the ingredients for optimum results.

In another bowl or jug, combine the mustard, apple cider vinegar, aquafaba, and water and whisk them together.

Pour the combined liquids into the dry ingredients and whisk together until smooth and bubbly. Pour into a jug to make pouring quick and easy, then leave to rest while you proceed with the next step.

While the batter is resting, prepare your muffin pans. They must be metal muffin pans and not silicone or ceramic, and they must be muffin pans and not shallow Yorkshire pudding pans. If you use a pan with shallow wells this recipe will not work.

Add enough oil to give a depth of about 3 to 4mm, then swirl it around in the pan so it goes up the sides. Don't be tempted to use less oil as the recipe won't work as well. Put the oiled muffin pan in the oven on the old baking tray that preheated in the oven until it's literally smoking hot. This should take about 10 minutes.

You need to work very quickly now. Make sure your jug of batter is right next to you as you open the oven. Very quickly, but very carefully, remove the baking tray & muffin pan from the oven, making sure to close the door immediately to keep the heat in. In a long, thin stream, pour the batter into the hot oil in each well of the pan. You need to fill them nearly to the top. The oil will rise above the batter. Stop pouring once the oil is just about level with the rim. You need to do this really quickly because you need to keep the heat in the pan for the puddings to work well. As soon as the wells are all full, put the pan (on the baking tray) right back into the oven and shut the door quickly. Do not open the oven door, not even for a quick peek until you are at least past 25 minutes of cooking or they will collapse.

Cook the puddings for at least 30 minutes, or up to 40 minutes for more dried-out, crispy puddings. I like them a little gooey inside and 30 minutes is about right. If you prefer them dryer again, turn the oven right down and let them cook a bit longer. Do not open the oven door, not even for a quick peek until you are at least past 25 minutes of cooking.

Remove the puddings from the oven and serve immediately.