Boil the potatoes in water for about 20 minutes or until they are soft, but not over cooked and mushy.
Once they are cooked drain well, add in the egg yolks, butter and a little salt and pepper.
Mash until they are smooth and soft, but don't overdo it or they will get sticky and glue like.
Add the mashed potatoes to a piping bag fitted with a wide star tip, a 1M tip is what I use. If you do not have a piping bag you could try adding the potatoes to a ziplock type bag and cut the corner off and try piping it out of that.
Pipe onto the parchment lined pan to make small swirly shapes.
Bake in the oven for about 20 minutes until they turn a little brown on the edges.