Cut potatoes in half and place into a large stockpot over high heat. Add a teaspoon of sea salt.

Cook the potatoes under tender, about 20 minutes.

Drain the potatoes, and place them into the bowl of a stand mixer fitted with the whisk attachment.

Add heavy cream, whole milk, and softened butter, rosemary, grated cheeses, sea salt, freshly cracked black peppercorns.

Whisk potatoes until all of the ingredients and fully incorporated.

Taste the potatoes and adjust the seasoning to your liking.

Serve.