Peel and dice the potatoes into bite-sized pieces. Place them in a large saucepan, cover with water, and bring to a boil over medium-high heat. Cook until tender when pierced, about 12 to 15 minutes. Drain and set aside.

In a separate large pot, add chicken stock, cold water, diced sweet onion (if using), diced green onion, salt, and black pepper. Bring to a gentle simmer over medium heat and allow to cook for 20 minutes to enable the flavors to meld.

In a medium saucepan, melt the butter over medium heat. Gradually whisk in the flour and cook, stirring constantly, until a smooth paste forms and the raw flour flavor cooks out, about 2 to 3 minutes.

Slowly pour and whisk the roux into the simmering broth. Stir thoroughly to integrate and thicken without forming lumps. Continue to simmer over medium heat.

Add the heavy whipping cream, mixing gently to combine. Allow the soup base to simmer for an additional 20 minutes, stirring occasionally for even consistency.

Return the cooked, diced potatoes to the soup. Stir in the shredded cheddar cheese and half of the crumbled bacon. Mix well so ingredients are evenly distributed.

Ladle into serving bowls and top with remaining bacon, extra cheddar cheese, and additional green onions. Serve hot for best texture and flavor.