In a large pot, heat over medium-high heat, add the Italian sausage, and sear until browned, about 6-8 minutes. Break it up into small pieces. Transfer the sausage to a paper towel-lined plate to drain excess fat, leaving drippings in the pot.

Lower heat to medium and add 1 tablespoon of unsalted butter into the same pot. Once melted, add the mirepoix and sauté for 5-10 minutes until soft and fragrant.

Stir in minced garlic, cooking for about 30 seconds until fragrant. Avoid burning the garlic.

Add chopped baby gold potatoes, dried parsley, dried basil, salt, and pepper to the pot. Pour in chicken stock and bring to a boil. Reduce heat to medium-low, cover, and let it simmer for 15-20 minutes until potatoes are fork-tender.

In a separate pot, melt remaining 4 tablespoons of butter over medium heat and whisk in the flour. Gradually pour in 3 cups of milk, whisking continuously until thickened, about 5 minutes. Stir in heavy cream and remove from heat.

Once potatoes are tender, mix in the creamy mixture and shredded Cheddar cheese until melted. Return cooked sausage, heating through and adjusting seasoning to taste.

Ladle soup into bowls and serve warm with a slice of buttered bread.