Wash the baby Yukon Gold potatoes.
Heat the sous vide water to 194°F/90°C.
Place the potatoes, rosemary, salt and garlic powder in the sous vide bag.
Close the bag and shake to distribute the seasonings.
Lay the bag flat on the counter to arrange the potatoes in a single layer.
Add the 3 tablespoons of butter on the potatoes.
Vacuum and seal the bag.
Place the bag in the water and weigh the bag down.
Cook the potatoes for 1 hour.
Remove from the water and press the potatoes with a coffee mug to smash them while still in the bag.
Heat a cast iron skillet to smoking hot.
Add olive oil to the skillet.
Place the pressed/smashed potatoes in the oil and fry for 2-3 minutes per side or until desired crispness is achieved.
Serve with additional salt and rosemary.