Fill a large stock pot three quarters’ full with water, cover and put on the stove to boil over high heat. While the water heats up, peel potatoes, rinsing them before cutting each into large chunks.
Drop the potato chunks in boiling water with the salt. Bring water back to a boil again, before turning burner down to a simmer. Simmer potatoes for about 15 – 20 minutes, at which point the potatoes should be just fork tender.
While the potatoes simmer, put the cream and butter in a heatproof (nonmetal) bowl and microwave the mixture for 45 seconds. Ingredients will be warm and beginning to melt. Add black pepper to the creamy butter mixture before setting aside.
When potatoes are fork-tender, remove from heat and drain the water from the pot. Transfer potatoes to the bowl of a stand mixer that has been fitted with its whisk attachment. Add cream mixture to the bowl and beat on the lowest speed until ingredients are well combined (but the potatoes are still halfway lumpy). Use a spatula to scrape down the sides of the bowl.
Cut the Boursin cheese into at least a dozen smaller pieces and add the pieces to the potato mixture. Beat potatoes on low again until cheese is fully incorporated and the mixture is smooth. This happens quickly, only 30 – 45 seconds. (Be careful to not overbeat, lest the potatoes develop an unappetizing, glue-like texture.)
Serve potatoes while piping hot.