Peel the potatoes and cut into even-sized chunks (about 1 1/2-inch or 4 cm). Add them to a large pot along with peeled cloves garlic (don't worry, the dish won't be too garlicky). Pour cold water to cover the potatoes. Season the water well with salt. Bring to a boil then simmer for about 10-15 minutes or until the potatoes can be easily pierced with a fork.
5 lbs (2.2 kg) Russet potatoes, 8 cloves garlic
While the potatoes are cooking, cook the bacon until crispy: either in a 400°F (200°C) oven for about 13-18 minutes (see this post for detailed instructions) or in a skillet on the stovetop (I prefer baking bacon). 5 oz (145g) bacon
Drain the potatoes on a sieve then return to the pot. Cook over low heat for 30-60 seconds, stirring, until all the remaining moisture is evaporated. Take off the heat.
Prepare a 9x13 inch (23x33cm) baking dish. Preheat the oven to 350°F (180°C).
Mash the potatoes and garlic cloves using a potato ricer or potato masher (potato ricer is best for fluffy mashed potatoes) directly into the baking dish.
Make brown butter: Add butter to a medium saucepan and cook it over medium heat until it's melted, then cook for 2-3 more minutes or until it's golden brown and smells nutty. It should be just light golden brown and not dark golden brown. Reduce the heat when you see it's starting to brown to avoid burning it.
1 stick + 2 tablespoons (145g) butter
Add the brown butter to the potatoes and stir to combine.
Add sour cream, cream cheese, milk, and heavy cream to the same pot. Whisk until smooth and cook until very hot but not boiling.
1 cup (240ml) sour cream, 4 oz (115g) cream cheese, 3/4 cup (180ml) heavy cream, 3/4 cup (180ml) milk
Add the mixture to the potatoes and stir until combined. It will look soupy at first but the potatoes will absorb it all. Shred cheddar on the large holes of a box grater. Fold in about 1/3 of the shredded cheddar and season with salt to taste (if it's missing some flavor, usually you just need to add more salt). 2 cups (200g) sharp cheddar cheese, salt and pepper to taste
Even out the surface with a spatula. Top with the remaining cheese.
Cover the baking dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for a further 10 minutes or until hot and bubbly.
Take out of the oven and top with cooked crumbled bacon. Put in the oven for 2-3 more minutes to warm up the bacon. Sprinkle with chives just before serving.
1/4 cup chopped chives
Enjoy!