Boil the Yukon Gold potatoes until they're soft.
Let them cool slightly, then dice them up.
In a large pot, melt the butter over medium heat.
Add the diced potatoes and stir well.
Pour in the milk, sour cream, and heavy whipping cream.
Stir continuously as it heats up to avoid sticking.
When the mixture starts to simmer, add the russet potatoes to the pot.
Mix in the chicken broth for added flavor.
Sprinkle in the Potato Slayer seasoning.
Serve the soup hot, garnished with green onions.