Cut potatoes into 1-inch cubes and pat dry with paper towels. Slice sausage into rounds. Dice onion and mince garlic. Shred cheese if not pre-shredded.

Heat 1 tablespoon olive oil in a large oven-safe skillet over medium-high heat. Add sausage and cook 4-5 minutes until browned on both sides, stirring occasionally. Transfer to a plate and set aside.

Add remaining 1 tablespoon oil to the skillet. Add onion and cook 3 minutes until softened. Add garlic and cook 30 seconds until fragrant. Add potatoes, ranch seasoning, and chicken broth. Stir to combine and bring to a simmer.

Cover and simmer over medium-low heat for 15-18 minutes, stirring once halfway through, until potatoes are fork-tender but not falling apart. Most of the liquid should be absorbed.

Stir in heavy cream and 1.5 cups shredded cheddar until melted and creamy. Fold in the browned sausage. Taste and add salt if needed - the ranch seasoning is fairly salty.

Preheat broiler to high. Sprinkle remaining 1/2 cup cheese evenly over the top. Broil 2-3 minutes until bubbly and lightly golden. Watch closely to prevent burning.

Let rest 5 minutes to thicken slightly. Garnish with fresh parsley and serve directly from the skillet.