Boil the Potatoes: Place the potatoes in the large saucier and cover with cold water. Add the salt and bring to a boil. Cook until fork tender.
2.2 lb yukon gold potatoes, 2 tsp kosher salt
Garlic Brown Butter: Add the butter and garlic cloves to the 1 qt saucier over low heat. Cook until the butter is golden brown, then remove from the heat. Remove and discard the garlic.
6 tbsp unsalted butter, 4 garlic cloves
Dry the Potatoes: Drain the potatoes and let them sit in the colander for 10 minutes. Pass them through the potato ricer, then through the tamis strainer. Return to the saucier over medium-low heat for 1 to 2 minutes to cook off excess moisture. Remove from the heat and cool for 5 minutes.
Mix: Add 3 tbsp of the garlic brown butter, the egg yolks, Parmesan, white pepper, onion powder, and garlic powder to the potatoes. Mix until fully incorporated. Season with salt.
3 egg yolks, 3/4 cup parmesan, 1/2 tsp white pepper, 1/2 tsp onion powder, 1/2 tsp garlic powder, kosher salt
Pipe: Line the sheet pan with parchment paper. Fit the piping bag with the star tip and fill with the potato mixture. Pipe a small dollop onto the sheet pan and press a cube of gruyère into the center. Pipe the potatoes around the cheese to form a cone. Repeat to make 12.
6 oz gruyère block
Freeze: Place the sheet pan in the freezer for 15 to 30 minutes. Preheat the oven to 425°F (220°C).
Bake: Spoon the remaining garlic brown butter over the potatoes. Bake for 15 to 20 minutes, until golden.