Bring a large pot of water to boil. Then add in salt and potatoes. Allow to boil for 15-20 minutes, or until fork-tender.
While potatoes are boiling, put a large sauce pan on medium high heat. Add in butter and minced garlic. Saute until garlic is golden brown. Then add in heavy cream, milk, and garlic salt.
When potatoes are tender, drain the water completely, leaving potatoes in the pot. Add in butter and cream mixture into the potatoes. Add in Parmigiano Reggiano cheese.
Using a hand-held mixer, mix on low until potatoes have been incorporated into the cream mixture. Slowly increase the speed and whip potatoes until they are completely smooth and creamy. Do not overmix or potatoes will become gluey.Optional: For best results, you can use a food mill to process the potatoes, and then use a whisk to incorporate the riced potatoes into the cream and butter mixture. But for most home cooks, a hand mixture should yield good enough results.
