Wash and peel your potatoes. Chop into large chunks (about 2 inch cubes).
Place your potatoes in a large pot and submerge in COLD water - this makes your potatoes less starchy. Add 1 tbsp of salt. Stir, start to boil. Keep your pot covered. Boil until fork tender, about 10 minutes (test before straining).
While boiling, start your cheese sauce. Cube your cheeses and mince your garlic gloves. Set aside.
In a large pan, melt 6 of your 7 tbsp of unsalted butter and melt on low until it starts to sizzle. Add the garlic to hot butter and saute until garlic is golden brown. Keep an eye on this as garlic will burn. Keep your heat on low-medium, your garlic should be sizzling. Let this saute for about 5 minutes until garlic is browned.
Add in 1 cup of heavy creamy and stir until combined. Once your cream is plenty hot, add in your cubed cheese in 2-3 portions. Let the first portion melt, add another handful, let melt, repeat. Check your potatoes with a fork (if your fork can easily glide through them, strain and set aside. If not, cook for a few more minutes).
Add white pepper and 1.5 tsp salt (cheese sauce will taste salty but will balance out once you mix with the potatoes - so don’t worry!).
Keep stirring, your cheese sauce should be thick - like a fondue cheese. Set heat to low and check your potatoes. If you hadn't already forked and strained, do so now.
Using a potato ricer, rice your potatoes into a large bowl (during this process, keep your cheese on low so it doesn’t thicken and cool).
Once your potatoes are riced, add your cheese sauce to the potatoes and mix well.
Give it a taste test once everything is combined and add salt, pepper, or garlic powder to taste!
Spray your baking dish (this helps to brown the edges) and scoop your potatoes into an oven safe dish. Spread evenly. Melt 1 tbsp of butter and using a pastry brush, brush the butter evenly onto the potatoes.
Bake for 20 minutes at 350. After 20 minutes, broil the potatoes for 3-6 minutes (this will vary from oven to oven). Keep an eye on this because broiling can burn quickly. Once golden brown on top, remove from oven and top with chopped chives. Enjoy!