In a large pot over medium heat, melt 2 tablespoons of unsalted butter until bubbly. Add 1 chopped onion and 2 minced garlic cloves, sautéing until the onion is translucent and fragrant, about 3-5 minutes.

Next, add about 4 cups of diced russet potatoes and 4 cups of chicken or vegetable broth to the pot. Increase the heat to bring the mixture to a gentle boil.

When the mixture boils, reduce the heat to low and simmer uncovered for 15-20 minutes, or until the potatoes are tender and easily pierced with a fork.

Use a potato masher to mash some of the potatoes for a creamy texture, or carefully blend half the soup until silky and return it to the pot.

Stir in 1 cup of milk, ½ cup of heavy cream, and 1 cup of shredded sharp cheddar cheese. Simmer gently for about 5 minutes, stirring frequently, until the cheese melts.

Season with salt and black pepper to taste, and serve hot, garnished with crumbled bacon and chopped fresh chives or green onions.