You'll need the oven set at 200 C/ 395 F. Prepare a lined baking tray
Mix the yeast with the tepid water and the sugar and set aside somewhere warm (10 min)
Put the flour and salt into a bowl and whisk together to mix
Your yeast should be bubbly and frothy now, stir.
Mash the cold sweet potato and mix with the milk gradually then add the yeast water and butter and mix to combine.
Make a well in the centre of the flour and pour in the liquid. Mix till all of the flour is combined.
Mark the dough into quarters. Each quarter should make 6 slider buns. Roll the buns with plenty of flour on your hands, rubbing off excess sticky dough as you go. Clean hands will make the dough much easier to roll. Put each bun onto the lined tray.
Now cover the tray with another piece of baking paper and leave in a warm place for 30 to 40 minutes. ( plastic wrap will stick to the buns)
The buns should double in size. Pop them into the oven ( I like to sit my tray on a pizza stone to cook the bottom quicker, but if you don't have one don't worry)
Bake for 15-20 minutes or until golden and cooked through. (Turn one over to check the bottom). My oven is very cool. Adjust the timing to suit your oven. If it is fan forced they will take 10-15 minutes.