Preheat your oven to 375°F (190°C).
Wash and dice the Yukon Gold potatoes into bite-sized cubes.
Boil the diced potatoes in salted water for about 10 minutes until slightly tender but still firm.
Drain the potatoes and return them to the pot. Add the milk, sour cream, ranch dressing mix, garlic powder, salt, and pepper to the potatoes and stir gently until coated.
Fold in the cooked smoked sausage and half of the cheddar cheese into the potato mixture.
Transfer the potato mix to a greased baking dish.
Sprinkle the remaining cheddar cheese evenly over the top.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for about 5 minutes.
Garnish with chopped green onions before serving.