To prep the tatties and neeps, do the following.

Wash and peel the potatoes. Cut them into cubes about 1 1/2". Place in a pot of salted water. Boil the potatoes until tender, about 15 mins. Drain the water and mash the potatoes in the pot. Add 2 Tbsps. of butter and 1/4 to 1/2 c. of milk. If you have a handheld mixer, use it to blend in the butter and milk. Transfer to a serving bowl.

The turnip is prepared in the same way but omit the milk. I like to add a Tbsp. of brown sugar to my "neeps".

Good luck!