Dice russet or golden potatoes into bite-sized cubes. In a large pot, bring salted water to a boil, then add potatoes. Cook for 15-20 minutes until fork-tender. Drain and set aside.

In the same large pot, combine chicken stock, diced sweet yellow onion (if using), salt, pepper, and a splash of water. Bring to a simmer and cook for 20 minutes.

Melt 4 tablespoons of butter in a separate saucepan. Gradually whisk in 1/4 cup of all-purpose flour, stirring continuously until golden and bubbly, about 2-3 minutes.

Slowly pour the roux into the simmering stock while whisking vigorously to avoid lumps. Cook for another 5 minutes until slightly thickened.

Slowly stir in 1 cup of heavy whipping cream and simmer for 20 minutes, stirring occasionally.

Gently fold the cooked potatoes into the mixture and cook for an additional 5 minutes.

Ladle the soup into bowls, topping with crumbled bacon, shredded cheddar cheese, and chopped green onions. Drizzle with extra cream if desired.