Step 1

Melt the butter in a large skillet over medium heat. Once melted, add the sliced onions and kosher salt. Stir and sauté the onions. Adjust the heat down as needed so the onions do not burn or color but slowly cook. Continue to sauté the onions until they become dark and caramelize, 30-35 minutes.

Step 2

Remove from the heat and add the Worcestershire sauce and garlic. Stir and set aside.

Step 3

Preheat the oven to 350℉. Scrub the potatoes. Leave the skin on for a more rustic look, or peel if desired.

Step 4

Dice the potatoes into ½-inch pieces and place them in a 6-quart stockpot. Cover the diced potatoes with water, add a pinch of kosher salt, and bring to a boil. Once boiling, reduce to a simmer, cover, and cook until the potatoes are fully tender, 20-30 minutes.

Step 5

When the potatoes are tender, drain the water. Mash or mix the potatoes with a hand mixer until they are combined. Mix in the cream cheese, sour cream, and warm milk until the potatoes are smooth. Add the caramelized onions, black pepper, kosher salt, Parmesan cheese, and one cup of the Monterey Jack cheese.

Step 6

Pour the potatoes into a butter 9 x 13-inch baking dish and sprinkle with the remaining one cup of Monterey Jack cheese. Cover with foil and bake for 30 minutes. Remove the foil and bake until the potatoes are warmed throughout and the cheese is beginning to brown, 20-30 minutes. Remove from the oven and top with chopped chives for a garnish.