Check out the step by step photos above and more importantly the video below, it will help a lot! Halve the dough for two people.
Preheat your oven to 400f (200c).
Pierce each sweet potato with a sharp knife a few times on all sides.
Bake in the oven for 45 mins - 1 hour, turning half way through until a knife slides through. Don't overcook as they can go mushy.
When still warm scoop the insides out. I usually just cut a slice down the middle and the skin comes away easily.
Pass through a potato ricer onto a tray lined with paper towels. If you don't have a ricer then mash with a potato masher and lay in an even thin layer on the paper towels.
When the sweet potato has completely cooled, transfer to a mixing bowl.
Add the egg yolk and mix through roughly.
Add the salt and flour and with a fork mix it through (watch the video below!) I use the fork to cut back and forth through the mixture to keep it light.
Transfer to a piping bag or snaplock bag with a hole about 1.5cm. It can be refrigerated like this in the bag if you are making dough ahead.
Get a big pot of salted water boiling. Hold the bag so the tip is over the water (just the tip, not your hand or else the water will splash up on it)
Continuously squeeze the bag and using a pair of sharp scissors, cut the gnocchi off so they drop into the water. Do any length gnocchi you like, I normally aim for about 2cm.
This will have to be done in batches, I normally squeeze and cut for about 30 seconds then let them boil. You'll get faster the more you do it.
Let each batch boil until they float to the top then give them another 30 seconds before removing with a slotted spoon or spider strainer. Transfer to a tray and continue with the rest of the dough.
The gnocchi might seem slightly fluffy on the outside but that is because there is minimal flour used, it's a good thing!
Add them to any pasta sauce you like. I love crisping them up in a little olive oil in a non stick pan first then serving with a crispy sage brown butter. Check out my pan fried gnocchi in brown butter recipe!