Bring a large pot of salted water to a boil. Add the peeled, cubed russets and simmer until fork-tender, about 15–20 minutes.

Drain very well and let the potatoes sit in the colander a few minutes so excess steam escapes.

Pass the hot potatoes through a ricer or mash them gently until smooth.

Add the softened butter, warmed heavy cream, egg yolks, garlic powder, onion powder, and salt and pepper. Mix just until combined.

Preheat the oven to 425°F (220°C). Line a baking sheet and lightly grease with olive oil.

Fit a large piping bag with a star tip and fill it with the potato mixture. Pipe 2–3 inch rosettes onto the prepared sheet, leaving space between each.

Bake for 15–20 minutes until the edges are golden and the bottoms are set.

Optionally broil for 1–2 minutes for extra color, watching closely to avoid burning.