Start by preheating the oven to 150 degrees Celsius (302 degrees Fahrenheit) (conventional oven). 

Scrub the potatoes and boil them for 10 minutes in generously salted water. Give the rosemary sprigs 5 seconds in the water as well.

Let them steam off for at least 10 minutes before continuing cooking in the oven.

Find a baking dish and place the rosemary sprigs, salt, and pepper in it, then toss the potatoes around in it.

Give the potatoes 1 hour in the oven, then turn them over and give them another hour.

The potatoes are now soft on the inside and deliciously crispy on the outside.