Begin by heating a large pot over medium-high heat. Add Italian sausage, breaking it up as it cooks for about 5-7 minutes until it’s deeply browned and cooked through. Transfer the sausage to a paper towel-lined plate, leaving some grease in the pot.

In the same pot, lower the heat and add 1 tablespoon of unsalted butter. Once melted, toss in the mirepoix and sauté for 5-7 minutes until softened and fragrant. Add minced garlic and cook for an additional 30 seconds.

Stir in chopped baby gold potatoes, dried parsley, dried basil, salt, and pepper. Pour in chicken stock, bringing to a rolling boil. Reduce heat to a simmer, cover, and cook for about 15-20 minutes until the potatoes are tender.

In a separate small pot, melt remaining butter over medium heat. Whisk in flour and cook for about 1 minute to form a roux. Gradually add milk while whisking until thickened. Stir in heavy cream off the heat.

Return to the pot with potatoes and vegetables. Slowly add the cream mixture, stirring well. Gradually incorporate extra-sharp cheddar cheese until melted. Adjust seasoning if needed with salt and pepper.

Gently stir in sour cream right before serving. Ladle into bowls and serve warm, ideally with hearty buttered bread on the side.