In a bowl, use a fork or spoon to loosen up the leftover mashed potatoes.
Mix in the flour, nutritional yeast, baking powder, plant-based milk or water, and a pinch each of salt and pepper. Stir together until all the ingredients are combined, then mix in the sliced spring onion. You should have a firm, fairly dry dough that keeps its shape, doesn't break apart, and can be easily moulded in your hands.
Note: You can either shape all of the potato cakes before frying, or do it in batches as you go.Take a small amount of dough – approx. one twelfth of the mix – and roll it into a ball. Flatten the ball into a disc approx. ½ inch thick and smooth the sides to make it round. Repeat until you've used up all the dough (I ended up with 12 pancakes, but this can easily vary).
Heat a wide, flat-based pan on medium heat and add a tablespoon of plant-based butter or oil. Once hot, place 3-4 pancakes in the pan (depending on how much space you have).
Gently fry for a few minutes until golden underneath, then flip over and repeat on the other side. Do this until you've used up all your dough, adding as much extra plant-based butter or oil as necessary for each new batch.
If you like, you can place the cooked pancakes on a plate lined with kitchen paper to remove any excess oil. Serve warm with your favourite toppings or accompaniments.
